EDUCATOR’S GUIDE Harvard-Smithsonian Center for Astrophysics
Museum of Science, Boston
Cosmic
Questions
Our place in space and time
Cosmic
Questions
Our place in space and time
Table of Contents
Introduction to this Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Introduction to the Exhibit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Goals of the Exhibit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Cosmic Questions Exhibit Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
National Science and Math Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Classroom Activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
What are Your Ideas About the Universe? Cosmic Survey. . . . . . . . . . . . . . . . 9
Modeling the Universe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Exploring the Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
A Multi-Wavelength Exploration of the Universe . . . . . . . . . . . . . . . . . . . . . 29
Modeling the Expanding Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Evidence for the Expanding Universe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Is There Life on Other Worlds? The Drake Equation. . . . . . . . . . . . . . . . . . . 59
Is There Life Out There? Community Survey . . . . . . . . . . . . . . . . . . . . . . . . 65
Visiting the Cosmic Questions Exhibit. . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Your Cosmic Questions–Partner Interviews . . . . . . . . . . . . . . . . . . . . . . . . . 71
Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
“The universe is made of stories,
not atoms.”
– Muriel Rukeyser
20th
c. poet
Acknowledgments
Cosmic Questions: Our Place in Space andTime was developed by the Harvard-Smithsonian
Center for Astrophysics, a collaboration of the Smithsonian Astrophysical Observatory and
the Harvard College Observatory.The exhibit was designed by Jeff Kennedy Associates and
its national tour is managed by the Association of Science-Technology Centers. Supporting
educational programs and materials, including this guide, were developed by the Museum
of Science, Boston. Cosmic Questions has been made possible by the generous support of
the National Science Foundation and the National Aeronautics and Space Administration.
EDUCATOR’S GUIDE grades 7–12
Special thanks to Loren Stolow, Erika Reinfeld,
Marianne Dunne, Cathleen Clemens, Mary Dussault,
Lindsay Bartolone, Dr. Irene Porro, Dr. Simon Steel,
Dr. Jennifer Grier, TERC, and the many other
scientists and educators who contributed to this
guide. Educator guide graphic layout by Susan
Sutherland Designs.
Instructions for downloading or ordering this guide
can be found at http://cosmicquestions.org.
Cosmic Questions Educator’s Guide 3
INTRODUCTION TO THIS GUIDE
The Cosmic Questions Educator’s Guide is a resource for teachers of students in grades 7–12. A wealth
of excellent astronomy and astrophysics curricula has been developed by many educational, research
and government agencies. We have drawn from these existing resources and assembled activities that
best introduce and teach the complex concepts presented in the Cosmic Questions exhibit. This is not
intended to be a comprehensive curriculum. Resources are listed that direct you to more information.
The guide was developed in conjunction with the exhibit and complements a Museum visit. However,
the activities can also be used independently. The format is flexible, and you can pick and choose the
materials that are most appropriate for you.
The Guide includes:
• information about the Cosmic Questions exhibit.
• activities to do with your class before or after you visit the exhibit.
• activities to do during a visit to the exhibit.
• additional resources for exploring your own cosmic questions.
INTRODUCTION TO THE EXHIBIT
What is the universe like?
Was there a beginning to time?
How do we fit into the cosmos?
Ancient human questions remain at the heart of modern cosmology, the study of the universe as a whole.
This exhibit invites you to explore the emerging portrait of our magnificent universe. Like astronomers
who observe the galaxies in awe and wonder, you too just might find yourself asking new questions
about space, time and our place in the spectacular cosmos.
From interactive computer stations to stunning astronomical murals, the traveling exhibit Cosmic
Questions: Our Place in Space and Time takes visitors behind the scenes of modern cosmological science
and urges them to explore their own connection to the universe. Cosmic Questions has four thematic
areas: Our Place in Space; Observing the Universe; Our Place in Time; and Great Cosmic Mysteries. Each
area introduces new answers to old questions and inspires more questions that will further define ou
place in the cosmos.
GOALS OF THE EXHIBIT
Cosmic Questions employs a diverse set of exhibit experiences and interpretive strategies that invite visitors
to join the human quest to understand our place in space and time. The exhibit highlights new discoveries
in astronomy while providing visitors with opportunities to:
• Learn about key astronomical and scientific concepts, including:
> the composition of the universe and its vast scales of space and time.
> “learning from light,” the physical and analytical tools of the astronomer.
> the interplay of models, evidence and explanation in forming our understanding of
the universe.
• Increase their understanding of the nature of scientific inquiry by engaging in activities that
explore “how we know” about the universe.
• Encounter various human perspectives (historical, personal, cultural, artistic, etc.) on age-old
cosmic questions.
• Reflect upon their own ideas about the universe and the meaning and relevancy of the ongoing
human search for answers to cosmic questions.
Our Place in Space
In this introductory area, visitors
begin at our own Milky Way galaxy
and travel outward to billions of
galaxies as far as our eyes can see.
The question of how we fit into the
vast web that is our universe has
intrigued observers for many centuries.
It is with modern tools and
instruments that we are beginning
to truly understand how vast the
universe really is and how important
our questions are.
Welcome Home gives scale and
context for our place in our local
“cosmic neighborhood” using a large
mural of the Milky Way and our nearest
neighbors. Explore an interactive
map and a tactile bronze model with
audio narration.
Mapping the Universe shows how our
ideas about our place in the universe
have been expanding throughout time
with a display detailing the human
quest to map our place in the cosmos.
View the universe of galaxies in 3D
using a stereo viewer; see an astrolabe,
a kind of instrument used by
astronomers 1000 years ago.
Wall of Galaxies illustrates that the
Milky Way is just one of billions of
galaxies in the universe with a photo
gallery of beautiful galaxies and galaxy
clusters beyond our local neighborhood.
Launch from Earth and journey
through the universe using state-ofthe-art
scientific visualizations of
the cosmos.
Human Reflections connects visitors
to various interpretations of cosmic
themes and allows them to reflect on
their own views. See artistic, spiritual
and intellectual reflections on universal
cosmic questions; listen in on a video
of artists and scientists; use a magnetic
word board to create your own
cosmic poetry.
Observing the Universe
In this highly interactive section,
visitors explore the universe using
the tools of some of the world’s
foremost ground-based and spaceborne
observatories. With help from
modern tools and the scientists who
use them, we see how to piece
together the story of the universe
using the faint light of deep space.
Mauna Kea highlights the ways we
observe the universe from Earth
through a multimedia exploration of
the Mauna Kea mountaintop in Hawaii,
with a special focus on the Gemini
Observatory. Use an interactive CDROM
to meet scientists who use and
operate Mauna Kea telescopes; see a
telescope mirror in the making; view
beautiful telescope images; and control
a telescope yourself — request an
image to be taken tonight and emailed
to you tomorrow!
Chandra highlights the ways we
observe the universe from space with
a multi-media exploration of the
Chandra X-ray Observatory. Use an
interactive CD-ROM to meet scientists
who use and operate Chandra; examine
a model of this new space telescope;
view beautiful x-ray images of the
universe.
Multi-Wavelength Astronomy shows
how astronomers use different parts of
the electromagnetic spectrum to learn
new things about the universe and the
objects in it. This area is an introduction
to the rainbow of light beyond
what our eyes can see and an exploration
of what different objects look
like in those wavelengths. Use special
multi-wavelength viewers to explore
the night sky; compare different views
of stars, nebulae and galaxies on
CD-ROM with an astronomer as your
guide; listen to an audio analogy for
the electromagnetic spectrum.
Spectra Interactive demonstrates
what light tells us about an object
through a display about the information
contained in a star’s spectrum.
Use a real spectroscope to analyze the
light coming from different sources in
a simulated star field.
Infrared Astronomy shows how
infrared “eyes” can help us learn to
observe the world around us in new
ways. This multi-wavelength activity
highlights the infrared band of the
electromagnetic spectrum. Use a nearinfrared
camera to see phenomena
invisible to your eyes.
Sky-watchers,Then & Now illustrates
astronomical awareness throughout
history and across cultures, focussing
on observations of the supernova
explosion of 1054 A.D. Observe a
reproduction of an ancient Native
American bowl thought to document
the supernova’s appearance.
Beyond Hubble provides up-to-date
information about the latest developments
in space science. Use a
computer station and bulletin board
to explore current astronomy news.
Cosmic Questions Educator’s Guide4
COSMIC QUESTIONS EXHIBIT DESCRIPTIONS
5Cosmic Questions Exhibit Descriptions
Our Place in Time
Anchored by the Cosmic Kitchen
Theater, this area invites visitors to
reflect on the notion that our human
story is intimately linked to the
unfolding story of the universe.
Although life as we know it has only
existed for a brief moment of the
great cosmic history, we can look
back in time and examine the
expanding, evolving universe to
find our own connections to the
Big Bang.
Cosmic Kitchen introduces visitors to
their role in the story of the universe.
This short theatrical production
explores the 14-billion-year history of
the universe and the “recipe” for our
own existence. Go deeper into Carl
Sagan’s quotation, “if you wish to
make an apple pie from scratch, you
must first invent the universe.”
Cosmic Calendar highlights the major
events throughout the history of the
universe and how they relate to the
story of life as we know it. This giant
calendar shows the 14 billion year history
of the universe as if it occurred in
a single year. Which atoms in your
body are the oldest? Find out here.
The Big Bang guides visitors in thinking
about how we can examine and
understand conditions at the beginning
of the universe through a display
about the Big Bang scenario and the
evidence supporting it. Listen to
Einstein guide you as you explore 3D
models of “space-time”; peek into a
model of the expanding universe;
examine the evidence for a Big Bang;
and take an interactive journey
through time.
Great Cosmic Mysteries
While the other sections of this
exhibit invite visitors to explore what
we currently know and understand
about our place in space and time,
this area acknowledges that there are
deep mysteries yet to be understood.
A series of interconnected rooms
introduces a gallery of mysteries–
dark matter and energy, black holes
and the possibility of life elsewhere
in our universe. A fourth room invites
visitors to reflect upon their own
connections to the cosmos in a
unique and contemplative theater.
Connecting with the Cosmos gives
visitors the opportunity to make personal
and aesthetic connections to the
themes of the exhibit in a video minitheater.
Contemplate your connection
to the cosmos through words, music
and images.
What’s the Cosmos Made Of?
introduces visitors to the ideas of dark
matter and dark energy using a display
about the composition of the cosmos,
both observable and invisible. View
an eclectic sample of the 5% of the
universe we know about; see evidence
for the invisible world of subatomic
particles in a cloud chamber; examine
the evidence for unseen matter and
energy in the universe.
Are We Alone? engages visitors’
thoughts about other worlds and
displays information about the search
for extra-solar planets and the possibility
of life beyond Earth. Explore the
conditions for life in various parts of
the universe using a computer interactive;
enjoy historical views of other
worlds and artistic visions of newly
discovered extra-solar planets; compare
a model of an alien solar system
to ours.
What are Black Holes? familiarizes
visitors with the science around and
about black holes through an immersive
virtual exploration of black holes.
Take control of a spacecraft orbiting
a black hole; launch probes into the
black hole to explore its bizarre
behavior; learn about the anatomy
of and evidence for black holes.
What is the universe like?
Was there a beginning to time?
How do we fit into the cosmos?
Cosmic Questions Educator’s Guide6
NATIONAL SCIENCE AND MATH STANDARDS
The exhibit and these activities can be used to support the following National Science Standards*
Standards
Unifying Concepts and Processes
Science as Inquiry
Physical Science
Earth and Space Science
Science andTechnology
Science in Personal and Social
Perspectives
History and Nature of Science
Grades 5 – 8
Evidence, models and explanation
Understanding about scientific inquiry
Motions and forces
Transfer of energy
Earth in the solar system
Understanding about science and
technology
Science and technology in society
Nature of science
Grades 9 – 12
Evidence, models and explanation
Understanding about scientific inquiry
Motions and forces
Interactions of energy and matter
Origin and evolution of the universe
Understanding about science and
technology
Science and technology in local,
national and global challenges
Nature of scientific knowledge
Principles and Standards Grades 6 – 12
Numbers and Operators Understand numbers, ways of representing numbers, relationships among numbers and
number systems.
Algebra Understand patterns, relations and functions.
Use mathematical models to represent and understand quantitative relationships.
Analyze change in various contexts.
Geometry Specify locations and describe spatial relationships using coordinate geometry and other
representational systems.
Use visualization, spatial reasoning and geometric modeling to solve problems.
Measurement Understand measurable attributes of objects and the units, systems and processes of
measurement.
Data Analysis and Formulate questions that can be addressed with data and collect, organize and
Probability display relevant data to answer them.
Develop and evaluate inferences and predictions that are based on data.
Problem Solving Apply and adapt a variety of appropriate strategies to solve problems.
Communication Analyze and evaluate the mathematical thinking and strategies of others.
Use the language of mathematics to express mathematical ideas precisely.
Connections Recognize and apply mathematics in contexts outside mathematics.
Representations Use representations to model and interpret physical, social and mathematical
phenomena.
National Council of Teachers of Mathematics Principles and Standards**
* http://www.nap.edu/readingroom/books/nses/html/index.html
** http://standards.nctm.org/index.html
Classroom Activities 7
CLASSROOM ACTIVITIES
Cosmic Questions: Our Place in Space and Time is organized into four thematic areas. The activities in this
guide have been chosen to teach concepts presented in each of these areas.
1. Our Place in Space
• What are Your Ideas About the Universe? Cosmic Survey
• Modeling the Universe
These activities lay the foundation for thinking about the size and scale of the universe. They can
be used to assess students’ understanding and introduce concepts before a visit to the exhibit.
2. Observing the Universe, Learning from Light
• Exploring the Spectrum
• A Multi-Wavelength Exploration of the Universe
Everything we know about the universe beyond Earth we learn from light and electromagnetic
radiation. Astronomers use different parts of the electromagnetic spectrum to learn about the
universe and celestial objects. These activities assume students have some prior experience with
the electromagnetic spectrum. The first activity leads students through experiments with light
and filters, demonstrating that the broader the range of the electromagnetic spectrum we can
detect, the more information we gather. In the second activity, students work with spectacular
images taken with telescopes sensitive to different wavelengths of light. These activities are
appropriate before or after a visit to the exhibit. While visiting the exhibit students can see even
more stunning images of the universe.
3. Our Place in Time
• Modeling the Expanding Universe
• Evidence for the Expanding Universe
What does it mean to say the universe is expanding? How do we know the age of the universe?
What is the evidence for the Big Bang? Students will create conceptual models of the expanding
universe and use actual galactic spectra to calculate the movement of galaxies through space.
These activities could be introduced before a visit to Cosmic Questions and returned to in greater
depth after viewing the Cosmic Kitchen Theater and other information presented in the exhibit.
4. Great Cosmic Mysteries
• Is There Life on Other Worlds? The Drake Equation
• Is There Life Out There? Community Survey
The universe is full of mysteries that have no answers yet. These activities introduce students to
a framework for examining the possibility of life on other worlds, and connect to a visitor poll
about these same questions.
Each activity begins with connections to the Cosmic Questions exhibit, goals, and a list of materials.
Background for teachers offers information about the topic and tips for conducting the activity.
Suggestions for introducing the activity are included. Depending on students’ experience, some
activities may require teaching or review of concepts that are not covered in this guide, such as objects
in the solar system or the physics of light and electromagnetic radiation. Procedures provide step by
step instructions for the activity. Discussion notes serve as the basis for group discussions and help
students reflect on their learning. Student Worksheets and some suggested answers to the questions
presented in the activities are included.
The Resources at the end of the guide direct you to more information to help you get started or to
conduct further investigations on each of these topics.
A note about distances. We know that teachers often encourage students to use kilometers in their work. However, we have
included both kilometers and miles in this guide to provide an intuitive sense about distances in the universe. Because the
universe is so large, astronomers use the light year to express very large distances. A light year is the distance light travels
in a year, which is equal to approximately 6 trillion miles or 9.5 trillion kilometers.
Cosmic Questions Educator’s Guide8
9
WHAT ARE YOUR IDEAS ABOUT THE UNIVERSE? COSMIC SURVEY*
Exhibit Connections: Welcome Home, Mapping the Universe, Cosmic Calendar
Goal
• to introduce the concepts of the structure and evolution of the universe
Materials
For each student
• one set of seven Cosmic Survey images
• scissors
• one copy each of the three Cosmic Survey Student Worksheets–How Big? How Far? How Old?
Background
We could live in an infinite universe. No one yet knows the true size of our universe. Our view is limited
not by a physical edge to space, but by how far light has traveled since the time our universe was born.
The observable universe is just a portion of the whole.
Many people, adults and students alike, are familiar with the names of objects in space, but they have
an incomplete mental model of where those objects are in space, their relative size and scale, and how
they fit into the cosmic scheme of things. Understanding the sizes and distances of celestial objects can
be tricky because in our everyday experience, the stars all seem the same distance away, and the moon
can appear close or far away depending on whether you observe it near the horizon or higher in the
sky. Most people’s knowledge of dim and distant objects such as nebulae and galaxies comes mainly
from images in books, where all the images are about the same size with no indication of scale.
In this activity, a three-part questionnaire launches students on discussions about where objects in
space are located, and when they formed. By physically manipulating images of objects in space,
students represent their own mental models of space and time.
When you lead discussions with students, please keep in mind that ideas and insights about the threedimensional
organization of the universe develop gradually. Getting the “right answer” is not as important
as the critical thinking skills that students develop as they confront the questions that arise as they
struggle with their mental models of the universe.
This survey can serve as a great assessment activity for you to find out how your students think about
the universe, and you can use it to help design follow-up activities to improve their understanding.
Suggestions for Introducing the Activity
This is an introductory activity that guides students as they begin to think about where we fit in the
universe. Students should be familiar with the objects in our solar system and the terms for celestial
objects beyond our solar system. Ask students to name some objects in the universe. What might we
want to know about objects in the universe? What kind of information could we gather about objects
in the universe?
What areYour Ideas About the Universe? Cosmic Survey
* Images courtesy of NASA: Isaac NewtonTelescope; Smithsonian Astrophysical Observatory.
©2001 Smithsonian Astrophysical Observatory.This activity was developed with support from
NASA Grant No. NCC5-261. Universe! Education Forum. http://cfa-www.harvard.edu/seuforum.
Cosmic Questions Educator’s Guide10
Procedure
• Make enough copies of the Cosmic Survey images for each student to have a set of seven
images. You do not need to cut these images from the book; a separate set of both the large
and small images are found in the pocket at the back.
Part 1. What are your ideas?
• Hand out copies of the three data sheets and the sets of seven images. Have students
cut the images apart so they can physically manipulate them as they fill out their data
sheets. They should answer the survey questions in the following order: How Big?
How Far? How Old? (This order represents increasing levels of conceptual difficulty
for most students). Collect the students’ papers so you can look over their ideas.
• Organize the class into discussion groups of three to five students. Give each group a set
of survey data sheets. Explain that each team is to discuss the three survey questions and
come to an agreement, if possible, on the best order of images for each question. One
member of each team should record questions that arise as they order the images.
• Circulate among the groups of students, encouraging them to discuss any disagreements
fully and to write down arguments in support of their answers.
Part 2: Discussion
• Lead the class in a discussion about the 3 different survey questions. Play the role of
moderator, requiring each group to explain why they chose that order. (Ensure that
students are also comfortable saying, “we really didn’t know about these objects.”)
See the discussion notes for “correct” answers and frequent student ideas.
• After discussing each question, poll the students on the alternative orders of images
suggested. Do not announce the correct order at this time; students should be encouraged
to think for themselves.
• After getting a class consensus on all three questions, let students know the correct
answers and observations of astronomers.
• Try this activity again with your students after a visit to the Cosmic Questions exhibit or
as a post-astronomy unit assessment, to see whether their ideas and understanding
have changed.
Discussion Notes
Question 1: How Big?
The correct order for the 7 images, from smallest to largest is:
Telescope 40 feet long (12 meters)
Moon 2 thousand miles diameter (3,200 kilometers)
Saturn 75 thousand miles diameter (121,000 kilometers)
Sun 875 thousand miles diameter (1,408,000 kilometers)
Pleiades 60 trillion miles across the cluster (1 x 1014
kilometers)
Galaxy 600 thousand trillion miles across (1 x 1018
kilometers)
Hubble galaxies 600 million trillion miles across the cluster (1 x 1021
kilometers)
It’s hard to tell the size of objects from many of the images we see because they look about the same
size in the pictures. But the Sun is much larger than Saturn or any of the planets. In fact, a million
Earths would fit inside the Sun. Size counts in nature. Objects much larger than Saturn or Jupiter are
fated to turn into stars such as our Sun. They collapse under their own weight and grow fiercely hot as
their nuclear fires are kindled.
Students may also wonder whether in the image of the Pleiades, we are talking about the sizes of the
individual stars, or all the stars in the picture. For this picture and the Hubble galaxies, the challenge is
to figure out the relative size of the “field of view” – all the stars or galaxies in the cluster.
What areYour Ideas About the Universe? Cosmic Survey 11
Question 2: How Far?
The correct order for the seven images, from closest to Earth to farthest, is:
Telescope 350 miles above surface of Earth (560 kilometers)
Moon 250 thousand miles (402,000 kilometers)
Sun 93 million miles (1.5 x 108
kilometers)
Saturn 120 million miles (at its closest) (1.3 x 109
kilometers)
Pleiades 2,400 trillion miles (4 x 1015
kilometers)
Galaxy 200 million trillion miles (3 x 1020
kilometers)
Hubble galaxies 30 billion trillion miles (5 x 1022
kilometers)
Figuring out the relative distances of the Sun and Saturn requires knowledge about the relative orbits
of the planets. Depending on how much astronomy background students have had, the Pleiades may be
placed inside the solar system or as the farthest objects in space. In general, most students (and adults)
have a hard time understanding the relative distances of the last three objects.
Students often struggle with the distance of the Hubble Space telescope; after all, it takes images of
very distant objects. How far away is the Hubble Space telescope? Many people believe that it is
beyond the orbit of the Moon, but it’s actually only 350 miles high. That’s high enough for a clear view
above the Earth’s atmosphere, but low enough to enable it to be serviced by the astronauts aboard the
space shuttle.
Many people think the beautiful Pleiades cluster of stars must be further away than a cluster of galaxies,
because they look smaller. But all the stars we see in the night sky are much closer than even the
nearest galaxy. A galaxy is a “city” of many billions of stars. Galaxies are so far away that we can’t make
out the individual stars in them. In fact, the roughly 5,000 stars we can see with our naked eyes are just
among the closest of the billions of stars in our own galaxy, the Milky Way.
Question 3: How Old?
For this question, the correct order for the seven images is actually somewhat ambiguous, and the
subject of much current astronomical research! In confronting this seemingly simple survey question,
students are grappling with the big ideas of formation of the solar system, life cycles of stars, and
evolution of the universe! A best response, one that most astronomers––but not all—might give, is:
Telescope a few years (1990)
Pleiades 80 million years
Moon 4.5 billion years
Saturn 4.5 billion years
Sun 4.5 billion years
Galaxy 10 billion years
Hubble galaxies 10 billion years
We tend to think of stars as having been around for a very long time. In fact, our Sun is billions of years
old. But new stars, like those in the Pleiades, are continually being born. The Pleiades stars are only
about 80 million years old.
Which is older, the Sun or the Hubble galaxies? It depends on what you mean by “age.” The Sun is
about 4.5 billion years old. But the Hubble “deep-field” galaxies are among the most ancient and
distant objects we can see in the sky. The light from them has taken about 10 billion years to reach us.
So they were born long before our Sun. On the other hand, the Hubble deep field galaxies are young
galaxies! Because of light’s travel time, we see these galaxies as they were when they formed, only a
few billion years after the Big Bang. Many of the stars in the galaxies in this image may be younger
than our Sun, so we are looking at the “baby pictures” of objects that are now old.
Cosmic Questions Educator’s Guide12
You have been provided with images of seven different objects in space. Try arranging the pictures in order of actual size of
the object (or field of objects) pictured. Order the objects so that the smallest is on the top, largest is on the bottom. Write
down and keep track of questions that arise as you order the images.
When you are satisfied that you have the best order, record the names of the objects in the spaces below.
Objects Ordered by Actual Size
1.
2.
3.
4.
5.
6.
7.
Largest in
Actual Size
Smallest in
Actual Size
STUDENT WORKSHEET Cosmic Survey—How Big?
Question 1: How Big?
What areYour Ideas About the Universe? Cosmic Survey 13
STUDENT WORKSHEET Cosmic Survey—How Far?
Question 2: How Far?
You have been provided with images of seven different objects in space. Try arranging the pictures in order of distance of
the object from Earth. Order the objects so that the object closest to Earth is on the top, farthest is on the bottom. Write
down and keep track of questions that arise as you order the images.
When you are satisfied that you have the best order, record the names of the objects in the spaces below.
Objects Ordered by Distance from Earth
1.
2.
3.
4.
5.
6.
7.
Farthest
from Earth
Closest
to Earth
Cosmic Questions Educator’s Guide14
Question 3: How Old?
You have been provided with images of seven different objects in space. Try arranging the pictures in order of age, beginning with
the youngest (most recently formed) object and moving in order to the oldest. Write down and keep track of questions that arise
as you order the images.
When you are satisfied that you have the best order, record the names of the objects in the spaces below.
Objects Ordered by Age
1.
2.
3.
4.
5.
6.
7.
Oldest
Youngest
(Most Recently
Formed)
STUDENT WORKSHEET Cosmic Survey—How Old?
What areYour Ideas About the Universe? Cosmic Survey 15
COSMIC SURVEY IMAGES–LARGE
Cosmic Questions Educator’s Guide16 Cosmic Questions Educator’s Guide
COSMIC SURVEY IMAGES–SMALL
Moon
WhirlpoolGalaxy
HubbleDeepField
Galaxies
HubbleSpace
Telescope
Pleiades
StarCluster
Saturn
Moon
WhirlpoolGalaxy
HubbleDeepField
Galaxies
HubbleSpace
Telescope
Pleiades
StarCluster
Saturn
Moon
WhirlpoolGalaxy
HubbleDeepField
Galaxies
HubbleSpace
Telescope
Pleiades
StarCluster
Saturn
Moon
WhirlpoolGalaxy
HubbleDeepField
Galaxies
HubbleSpace
Telescope
Pleiades
StarCluster
Saturn
Sun
Sun
Sun
Sun
Modeling the Universe 17
MODELING THE UNIVERSE
Exhibit Connections: Welcome Home, Mapping the Universe, Cosmic Calendar
Goals
• to represent earth’s physical place in the solar system and universe
• to understand astronomical size and scale
• to understand strengths and weaknesses of models
Materials
• modeling clay
• paper
• balloons
• different sized balls and marbles
• string
• markers
• scissors
• straws
• other odds and ends that might be useful in creating models
• Copies of Universe Model Analysis Student Worksheet for each group
Background
Our Milky Way is just one of countless galaxies in the universe. Our view of the universe is expanding.
Less than a century ago, astronomers thought that our Milky Way galaxy of stars might be the
whole universe. Today, we can observe the splendor of galaxies far beyond our own. We can see the
estimated 100 billion galaxies that make up our “observable universe.”
In the 1980s, Margaret Geller and John Huchra began a survey of the distances to 25,000 galaxies.
To their surprise they found that galaxies are grouped in vast filaments and sheets. There appear to
be great voids where no galaxies are found. Today, teams of astronomers all over the world are
mapping thousands of galaxies, in search of clues about the size and shape of the cosmic web.
In this activity students are challenged to create a model of the universe in a single class period.
Getting a “big picture” of the universe as a whole is a difficult challenge — for professional
astronomers as well as for students — but it’s a challenge that has occupied humanity for
ages. To understand the vast ranges of scale of cosmic systems, the student of the universe
has to create and evaluate a variety of models against the observational evidence.
A model is a simplified imitation of something that we hope can help us explain and understand
it better. Models can take different forms, including physical devices or sculptures, drawings or
plans, conceptual analogies, mathematical equations, and computer simulations. In this activity,
students make a physical model to represent as much of the universe as they can. They will
then analyze their own and others’ models with regard to what they represent, what they
misrepresent, what they leave out, and perhaps most importantly, what questions they raise.
While the idea of creating a physical model of the entire universe in one class period can seem
a bit daunting, this activity quickly elicits student ideas and preconceptions about the contents
and organization of the cosmos. Most students will be somewhat familiar with solar system
objects, but may be confused about the relationship of stars to planets, and about the relative
distances. The scientist’s view of the hierarchical “nested” structure of the universe—planet
systems, star neighborhoods, galaxies, galaxy clusters—is not second nature to most people.
Suggestions for Introducing the Activity
This is an introductory activity that helps students think about where we fit in the universe,
and model the size, shape and relative position of objects in the universe. Students should be
familiar with the objects in our solar system and terms for celestial objects beyond our solar
system. This activity begins with students brainstorming about objects in the universe and the
concepts of models. Students with less experience with these concepts will require more time
and teaching in the discussion part of the activity.
Procedure
Part 1. Discussion
• Facilitate a class discussion of what’s in the universe. Ask students “What IS the
universe?” Brainstorm a list of objects in the universe that can be viewed with a
telescope. As students mention different objects, ask them what they know about
them. What is a planet? What is a star? What is a galaxy? How far away are these
things, relatively speaking? What do you think they would look like in the telescope?
Which ones can we see without the aid of a telescope? How could we group
the objects?
• Discuss how scientists use models to suggest how things work and to predict
phenomena that might be observed. Ask students to name some familiar models,
such as a globe, or a dollhouse. A model is not the real thing. It can always misrepresent
certain features of the real thing. Different models may represent only part of
what is being modeled.
Part 2. Modeling
• Divide students into groups of three or four. Each student can have one or more of the
following roles; model maker(s), recorder of model features, spokesperson.
• Challenge students to create a model of the universe in less than 30 minutes. You may
wish to have some groups choose just a part of the universe to model (such as the
solar system, or a galaxy, or perhaps just the earth-moon system). One person in the
group should write down the features of the model as it is built, along with questions
that arise.
• Students can use the Universe Model Analysis Student Worksheet to record the
features of their model as they work.
Part 3. Sharing Models with the Class
• As each group presents its model, ask the students to comment on these four
questions:
> What features of the universe does your model represent?
> What things does your model misrepresent?
> What things about the universe does your model omit, or not represent at all?
> What questions came up as your group worked on your model?
Discussion Notes
After sharing all the models, discuss the following questions.
Are there any patterns that emerge?
What parts of the astronomical models do you think represented the “real thing”
particularly well? Why?
What parts of the astronomical models do you think misrepresented the “real thing?”
Why?
Why is representing the whole universe a difficult challenge?
What are some things you need to find out to design a better model?
Cosmic Questions Educator’s Guide18
Modeling the Universe 19
STUDENT WORKSHEET Universe Model Analysis
A model is a simplified imitation of something that helps us understand it better. Because a model is not the real thing, it can
always misrepresent certain features of the real thing. Different models may represent only part of what is being modeled.
After your group creates your model, you will be asked to explain your model to the rest of the class, commenting on these
four questions:
What features of the universe does your model represent?
What things does your model misrepresent?
What things about the universe does your model omit, or not represent at all?
What questions came up as your group worked on your model?
Use this chart to record the features of your model as your group is working.
Features represented Misrepresented or Features of real thing
irrelevant features omitted by model
Questions we had:
Cosmic Questions Educator’s Guide20
Exploring the Spectrum 21
EXPLORING THE SPECTRUM
Exhibit Connections: Mauna Kea, Gemini Observatory, Chandra X-ray Observatory, Spectra
Interactive, Infrared Astronomy
Goals
• to demonstrate that the continuous spectrum of white light can be broken into many colors
• to experiment with how filters change the spectrum we perceive
• to demonstrate that the greater the portion of the spectrum you can perceive, the more
information you can gather
Background
What can light tell us about the universe? People tell stories. So does light. Astronomers are learning to
translate the tales light brings us from deep space. Explore some of the tools that help us understand what
the universe is trying to tell us.
This activity introduces students to the visible spectrum and then demonstrates what happens to an
image when certain wavelengths are blocked by filters or made visible using special tools. Astronomers
study the spectra of stars to learn many things, including how hot or cold stars are, whether they are
moving toward or away from us, and whether they have magnetic fields.
Students will gain a basic familiarity with the electromagnetic spectrum that will be useful for the
activities that follow in this guide. In the Multi-Wavelength Exploration of the Universe, students will
move beyond images in the visible spectrum to images of astronomical objects taken with telescopes
sensitive to different wavelengths of light. In Evidence for the Expanding Universe, students will
analyze spectra to investigate galactic motion.
Materials
• overhead projector
• diffraction grating
• cardboard
• colored pencils
• masking tape
A note about the filters:
We recommend the following filters. There are other companies besides Roscolux that supply Theatrical and Stage
Lighting Equipment. They will have different code numbers. Ask for pure color filters for science experiments.
Red medium red ROSCOLUX #27
Green dark yellow green ROSCOLUX #90
Blue primary blue ROSCOLUX #74
A note about the diffraction grating:
We recommend that teachers use a high-efficiency holographic diffraction grating. A more powerful grating
(with more lines per millimeter) is preferred. We suggest 750 lines per millimeter, available from Learning
Technologies, Inc., or Rainbow Symphony, Inc.
Suggestions for Introducing the Activity
Students should have some understanding of waves and the concepts of frequency and wavelength.
• whiteboard or large sheet of white paper
• red, blue and green filters
• transparency of three-circle RGB color diagram
• Exploring the Spectrum Worksheet
Cosmic Questions Educator’s Guide22
Procedure
• Find a dark space and cover windows as much as possible. This works best in a very dark room.
• Hand out copies of the Exploring the Spectrum Student Worksheet.
• Place the cardboard on the overhead so there is a slit approximately 1 cm. wide on the base
plate of the projector. Turn on the projector lamp.
• Place the diffraction grating in front of the upper lens and rotate the grating until the spectrum
appears on both sides of the projected slit on a large sheet of white paper or whiteboard.
• Ask students what they observe. How many colors are there in the rainbow? Can they see
separate colors? Have students draw what they see at the top of the worksheet.
• Label the colors with a black marker where they are projected on the whiteboard or white
sheet of paper.
• Ask students to predict what they think the spectrum will look like when viewed through a
red filter. On the Student Worksheet, have them draw their predicted spectrum.
• Place the red filter in front of the light and view
the spectrum. Is it as students predicted? Have
them draw the actual spectrum.
• Repeat with the blue and green filters.
• Use the overhead to project the diagram of overlapping
red, blue and green circles. What would
it look like if you could only see red and could
not see blue and green?
• Predict what the diagram will look like when
viewed through different colored filters. What
happens if you use two filters together?
• (Optional) Try this last exploration with photographs
or other color images. If you wish, you
may incorporate astronomical images.
Discussion Notes
Many students will incorrectly predict that the red filter will “turn” the whole spectrum red, and likewise
for the blue and green filters. This activity can help these students understand the idea that the
color is in the light, not the filter, and that the filters “subtract,” or absorb certain colors of light, while
letting other colors through.
Filters simulate what it is like if you can only see part of the full spectrum. In many ways humans
are “color blind.” Our eyes can see only the light emitted in the visible part of the electromagnetic
spectrum, just as the red filter only “sees” the red part of the diagram. The entire universe emits light
in every wavelength, so we must also look at it with telescopes sensitive to light that our eyes cannot
see. Different wavelengths of light can give us different information about the properties and features
of the object emitting that light. Continue with the next activity to investigate how astronomers use
multi-wavelength images to learn more about the cosmos.
masking tape
one-centimeter slit
black construction paper
(or cardboard)
large diffraction grating
overhead projector
Exploring the Spectrum 23
Full spectrum
Prediction: Spectrum when viewed through a red filter
Actual spectrum when viewed through a red filter
Prediction: Spectrum when viewed through a blue filter
Actual spectrum when viewed through a blue filter
Prediction: Spectrum when viewed through a green filter
Actual spectrum when viewed through a green filter
STUDENT WORKSHEET Exploring the Spectrum
Cosmic Questions Educator’s Guide24
25Exploring the Spectrum
RGB COLOR DIAGRAM
Cosmic Questions Educator’s Guide26 Cosmic Questions Educator’s Guide
ELECTROMAGNETIC SPECTRUM
visiblelightrays
microwaves
radiowaves
infraredrays
ultravioletrays
x-rays
gammarays
Electromagnetic Spectrum 27
Type of Radiation Description
Radio Radio waves are at the low end of the electromagnetic spectrum.They are
produced by electrons spiraling around magnetic field lines generated by
stars, galaxies and black holes.Their long wavelengths allow radio waves
to pass through a lot of the gas and dust in space that blocks shorter
wavelength light—hence we can probe deep into the hearts of celestial
objects by looking in the radio range.
Microwaves Microwaves are the short wavelength (high energy) end of radio waves.
Microwaves radiate from cool gas (cool here is close to absolute zero,
-273o
C!), such as the giant molecular clouds that become stellar nurseries.
We also sail in a sea of microwaves, the cooled radiation that is
the afterglow of the Big Bang itself. One percent of television static is
from this microwave background.
Infrared We think of infrared radiation as heat. More energy than radio but less
than visible light, infrared radiation is emitted by warm clouds of dust and
gas heated by nearby stars. Cool red stars, by far the most numerous type
of star, emit most of their light in the infrared. In fact, almost everything in
the universe, including people, is a source of infrared radiation.
Optical or A very narrow range of electromagnetic radiation is detectable by our
visible light eyes as visible light. Not only does the Sun have its peak output in this
range, but our oxygen/nitrogen atmosphere is completely transparent at
these wavelengths. We see planets in the visible because they reflect
sunlight; stars and hot gas emit visible radiation.
Ultraviolet Hot objects, such as the Sun radiate ultraviolet light (blocked, for the most
part, by our atmosphere). Some of the hottest stars shine more brightly in
ultraviolet light than in visible.The centers of many galaxies glow brightly
in ultraviolet light; it’s a telltale sign of gas heating up as it spirals closer
and closer to the central giant black hole.
X-rays X-rays are very high-energy radiation, with wavelengths no greater than
the diameter of an atom. X-rays are only produced in extreme environments
where gas temperatures are millions of degrees or particles are
traveling at close to the speed of light. Colliding galaxies, supernovae and
the intense gravitational fields around neutron stars and black holes are
the prime sources of x-rays.
Gamma rays Gamma rays are the very highest energy region of the electromagnetic
spectrum. Just as visible light is emitted from atoms when electrons
change their orbits, so gamma rays are emitted when the atomic nucleus
itself changes, such as in radioactive decay. Supernovae are a main
source of gamma radiation, when unstable radioactive elements created
in the violence of the explosion later decay.The supernova deaths of
the biggest super-giant stars create such extremes of temperature and
pressure that they can release a sudden flash of gamma radiation, called
a gamma-ray burst.
ELECTROMAGNETIC SPECTRUM
Cosmic Questions Educator’s Guide28
A Multi-Wavelength Exploration of the Universe 29
A MULTI-WAVELENGTH EXPLORATION OF THE UNIVERSE
Exhibit Connections: Multi-Wavelength Astronomy, Mauna Kea, Gemini Observatory, Chandra X-ray
Observatory, Spectra Interactive, Infrared Astronomy, What are Black Holes?
Goals
• to introduce images taken with telescopes sensitive to different wavelengths of light
• to understand that light carries information about physical features in the universe
• to demonstrate that because light of different wavelengths comes from different physical
sources, combining multi-wavelength images provides a more complete picture of the universe
Materials
This activity has several parts. Materials for each part are listed separately.
Background
New Eyes on the Skies
By using special telescopes that can detect wavelengths of light that our eyes can’t see, astronomers have
discovered objects in the universe we never knew were there. Stars being born, black holes, giant clouds of
gas surrounding entire galaxies—all these were discovered using telescopes that could see what our eyes
could not.
All telescopes collect light from objects in space. However, what we commonly perceive as light is only
one type of electromagnetic radiation. Radiation comes in a range of energies, spanning the electromagnetic
spectrum. The spectrum consists of radiation such as gamma rays, x-rays, ultraviolet, visible,
infrared and radio. Radiation travels in waves, like ripples on a pond. The energy of the radiation
depends on the distance between the crests (the highest points) of the ripple, or the wavelength. For
example, low-energy radio wavelengths can range from one centimeter (0.40 inches) to longer than
100 meters (the size of a football field)! High-energy x-ray wavelengths are no bigger than a single
atom. The shorter the wavelength, the greater the energy. Astronomers use telescopes that can detect
different wavelengths of light in order to gain a deeper understanding of what the universe is like.
In this activity, students will have the opportunity to use actual images taken with telescopes sensitive
to several of these wavelengths. Astronomers use images like these, combined with other information,
to develop a complete picture of the universe and the objects in it.
Suggestions for Introducing the Activity
Students should be familiar with the electromagnetic spectrum and understand the properties of
waves. See the previous activity, Exploring the Spectrum.
Cosmic Questions Educator’s Guide30
Part 1. Comparing Optical and X-ray images.
Materials
• transparencies of multi-wavelength images of the Crab Nebula and Eta Carinae cut into
four separate images
• overhead projector
Procedure
• Use an overhead projector or give small groups of students the four different multi-wavelength
astronomical images A, B, C, and D.
• Explain that these are actual pictures of two different astronomical objects. Two of the pictures
are of the Crab Nebula, which is a supernova remnant, the remains of an exploded star that died
in 1054 A.D. The other two pictures are of Eta Carinae, a massive star in the Carina nebula, that
scientists believe is about to explode as a supernova. Two of the pictures were taken with optical
telescopes. Two of the pictures were taken with an x-ray telescope.
• Ask students which two images they think show Eta Carinae and which two show the Crab
Nebula? Which two images were taken with optical telescopes? Which two were taken with an
x-ray telescope?
• Ask students to explain their choices. What evidence did they use to match the images?
• Now provide students with the following clues:
> The Crab Nebula optical image shows the shreds of a star that exploded.
> The Crab Nebula x-ray image shows a spinning pulsar within the heart of the nebula.
> The Eta Carinae optical image shows a central energetic star ejecting matter as an expanding
bubble of gas and dust.
> The Eta Carinae x-ray image shows arcs of high-energy gas around the star.
• Give students an opportunity to change their choices based on this additional information.
Discussion Notes
In the discussion about these images, it is more important for students to observe features than to get
the right answer. Astronomers use and compare multiple images to develop a more complete picture of
the universe.
The correct answers of which images are taken of which object by which type of telescope are as follows:
A - Crab Nebula optical image
B - Eta Carinae optical image
C - Crab Nebula x-ray image
D - Eta Carinae x-ray image
All of these images are in “false” color. The colors represent different wavelengths, but not necessarily
the colors we normally associate with visible light. Why would scientists use different colors? For more
information on false color see http://chandra.harvard.edu/photo/false_color.html.
What do you notice about the shape of the different images? Optical and x-ray images will give
different shapes.
These images are snapshots at one moment in time. Have Eta Carinae and the Crab Nebula always
looked this way? What do you think is causing the phenomena we observe? (Student answers may vary.)
This set of images, combined with other information, can help us develop a more complete picture of
the evolution of very massive stars. What else would you like to know about stellar evolution? For more
information about this topic, see the resources at the end of the guide.
A Multi-Wavelength Exploration of the Universe 31
Part 2: Analyzing Multi-Wavelength Images as Data
Materials
• multi-wavelength images of the Crab Nebula and Eta Carinae
• Student Worksheet–Analyzing Multi-Wavelength Images
• ruler
• scientific calculator
Background
To an astronomer, an image is more than just a pretty picture of an object in space—it’s data. The size
and scale of images tell astronomers about the relative sizes of features in each object. The brightness of
an image provides information about how hot or how abundant material in the object is. The shape and
form give clues about the structure of different features and the mechanisms at work within the object.
Procedure
• Give each student a set of the images of the Crab Nebula and Eta Carinae, a ruler, and Student
Worksheet. Use the images and calculators to answer the questions on the Student Worksheet.
Discussion Notes
Some questions are quantitative and answers will vary within an order of magnitude. Other questions
are qualitative and ask for student opinions. Answers will vary depending on the range of astronomical
knowledge students possess. The goal of this activity is for students to become familiar with the variety
of information contained in multi-wavelength images. Understanding the specific cosmic phenomena
shown is less important.
Suggested Answers
1. A sample chart appears below:
Additional observations
and questions
Lots of points
Busy
Looks like something
exploding
Something may be
spinning
Fuzzy
Why is it uneven?
Image
Crab Nebula,
optical (Image A)
Eta Carinae,
optical (Image B)
Crab Nebula,
x-ray (Image C)
Eta Carinae,
x-ray (Image D)
Observations about
shapes and forms
blob-like structure
strands or streaks
Like a bubble
Pinched in middle
Swirls with tails
Arc around a dot in center
One side is rounded, the
other is stretched out
Observations about
brightness
Streaks are brightest
Edges are dark
Brightest in center
Dark puffs with brighter streaks
Bright in center
Swirls are also bright
Brightest in center
Bright spots around edge,
especially in rounded part
Cosmic Questions Educator’s Guide32
2. 60 trillion miles (95 trillion kilometers)
3. 2003 – 1054 = 949 years ago
949 x 365 x 24 = 8,313,240 hours ago
60 trillion miles ÷ 8,313,240 hours ≈ 7,217,403 mph
(11,615,284 km/hr) (3,226 km/sec)
4. Student answers will vary.
Suggested answer: The material must have been moving much faster immediately after the
explosion. It has slowed down (decelerated) over time.
5. Students may have trouble seeing the jets and may measure from different points. The full extent
from tip to tip is about 3.6 light years (measured on these images using ratios), which is equal to
21 trillion miles (34 trillion kilometers).
6. Student answers will vary.
Suggested answer: The jets extend very far beyond the star. There must be a lot of energy coming
from the center of the image to generate such x-ray jets.
7. Our solar system is approximately the same size as the ejected material from Eta Carinae.
8. Student answers will vary depending on which “edge” students measure, from about 10 billion
miles (16 billion kilometers) to about 20 billion miles (32 billion kilometers).
9. 10,000 hours or 417 days or 1.14 years
10. Student answers will vary.
Suggested answer: The newly expanded material seen in the optical image would heat the gas
farther out causing it to glow. An x-ray image taken 1 year later would show a larger area of heated
gas, which might glow brightly in different locations than those seen in the current x-ray image.
The numbers quoted throughout this activity were taken from the following sources:
Diameter of the material in the optical image of the Crab Nebula from
http://www.seds.org/messier/m/m001.html
Diameter of the material in the optical image of Eta Carinae and speed of material around Eta Carinae
from http://hubble.stsci.edu/news_.and._views/pr.cgi.1996+23
Diameter of Crab pulsar from http://chandra.harvard.edu/press/crabfact.html
A Multi-Wavelength Exploration of the Universe 33
Use the set of optical and x-ray images of the Crab Nebula and Eta Carinae and the information below to answer the following
questions. For the purposes of this activity, assume all these images show these objects as they appear on January 1, 2003.
Diameter of the material in the optical image of the Crab Nebula: 10 light years
Diameter of the material in the optical image of Eta Carinae: 10 billion miles
Radius of Pluto’s orbit: approximately 4.6 billion miles (7.4 billion kilometers)
1 light year = approximately 6 x 1012
miles = approximately 9.5 x 1012
kilometers
1 mile = 1.6 kilometers
1. Examine the four images and record what you see:
Additional observations
and questions
Image
Crab Nebula,
optical (Image A)
Eta Carinae,
optical (Image B)
Crab Nebula,
x-ray (Image C)
Eta Carinae,
x-ray (Image D)
Observations about
shapes and forms
Observations about
brightness
2. A light year is the distance that light travels in a single year. How big is the Crab Nebula optical image, in miles?
(Kilometers?)
STUDENT WORKSHEET Analyzing Multi-Wavelength Images
Cosmic Questions Educator’s Guide34
3. The star that created the Crab Nebula exploded in 1054 A.D. If the material we now see originated in a single point,
how fast would the gas have to be moving to have reached the distance you just calculated in Question 2. Calculate
the velocity in kilometers per second. Assume no acceleration or deceleration. This gives you the average velocity.
4. Scientists now measure the gas to be moving at 1,800 kilometers per second. How does this compare with your
answer above? What can you conclude about this expanding cloud of gas?
5. The optical and x-ray images of the Crab Nebula are printed at the same scale. Look for two jets coming out from
the bright spot in the center of the x-ray image. How far do these jets extend, in light years? Miles? (Kilometers?)
6. Scientists believe the spinning star at the center of the Crab Nebula is now only 12 miles in diameter. Given this
information, how might you explain the huge jets you see in the x-ray image?
7. The Eta Carinae optical image shows a central energetic star ejecting matter as an expanding bubble of gas and dust.
How does the size of our solar system compare with the size of the ejected material in the optical image?
8. The x-ray and optical images of Eta Carinae are printed at the same scale. How far out from the central star does the
arc in the x-ray image extend, in miles? (Kilometers?)
9. If the material from the center of the star is accelerating outward at 1.5 million miles per hour, how long will it take for
the material visible in the optical image to reach the extent of the x-ray image?
10. As Eta Carinae continues to eject material, this material heats up the surrounding gas, causing it to glow in an x-ray
image. What do you think the x-ray image will look like in one year?
STUDENT WORKSHEET Analyzing Multi-Wavelength Images (continued)
A Multi-Wavelength Exploration of the Universe 35
Part 3: Getting a More Complete Picture Using Four Types of Images.
Materials
• transparent overlays for Centaurus A (cut the page to separate the four images)
• overhead projector
Procedure
• Use an overhead projector to display images of the Centaurus A galaxy. Show each
image one at a time. Ask students what they observe, reminding them to pay close
attention to relative size, shape and brightness.
Optical Image: This shows a large galaxy with a giant dust lane across the center.
Infrared Image: This shows the same galaxy with a very bright center.
Radio Image: This shows two huge lobes of gas and a bright spot in the center.
X-ray Image: This shows a bright streak, which represents a giant jet of
high-energy gas and many bright spots.
• Use the images in the following patterns to develop a more complete understanding of
what is happening in Centaurus A. As you place each image, or combination of images,
on the overhead, ask students what they notice. Use the symbols at the corners of the
images to align the images as you lay them on top of each other.
1. Place the Centaurus A optical image on the overhead and overlay with the infrared
image. Both images show a galaxy with a dust lane across the center. The infrared
image allows us to see through the dust lane to a bright spot in the center.
2. Remove the infrared image and overlay the optical image with the radio image.
The lobes of gas extend far beyond the center of the galaxy.
3. Remove the radio image and overlay the optical image with the x-ray image.
The high-energy jet runs perpendicular to the dust band.
4. Remove all the images. Place the radio image on the overhead and overlay the
x-ray image. The lobes of gas line up with the high-energy jet.
Cosmic Questions Educator’s Guide36
Discussion Notes
Again, the goal of this activity is for students to recognize how multiple images provide a
more complete picture, rather than to identify specific astronomical phenomena. Students
should not be expected to independently determine the story of the images described here.
This explanation is the result of many astronomers’ collaborations over many years.
The optical and infrared images of Centaurus A show a galaxy shining by starlight. Only when
we view Centaurus A at other wavelengths do we realize that most of its radiation is being
produced by something radically different. X-ray and radio images reveal a source of extreme
power at the center of the galaxy, something very small but capable of shooting jets of radiation
across millions of light years of space. The only mechanism now known to have this capability
is the intense gravitational and magnetic fields of a supermassive black hole.
The current model for the anatomy of a black hole
Inside a black hole the known laws of nature break down.
Look for the edge of the black hole at the center of the
illustration.
Matter approaching the black hole spirals in, gains energy and
heats to millions of degrees, forming a relatively flat disk of
gas and dust. Look for the flat accretion disk around the edge
of the black hole.
Some matter near the center of the black hole is hurled outward
at nearly the speed of light. Look for jets perpendicular
to the plane of the accretion disk.
This set of images of Centaurus A, combined with other information,
helps us develop a more complete picture of the structure
of galaxies. Scientists now believe supermassive black
holes reside at the center of most galaxies, including the Milky
Way. Multi-Wavelength images provide clues about the nature
of black holes and the giant jets being emitted from these
powerful objects.
A Multi-Wavelength Exploration of the Universe 37
CRAB NEBULA AND ETA CARINAE IMAGES
Cosmic Questions Educator’s Guide38
CENTAURUS A IMAGES
Centaurus A
optical
Centaurus A
radio
Centaurus A
infrared
Centaurus A
x-ray
Modeling the Expanding Universe 39
MODELING THE EXPANDING UNIVERSE
Exhibit Connections: Cosmic Calendar, The Big Bang
Goal
• to visualize a universe expanding in all directions
Materials
This activity has several parts. Materials for each part are listed separately.
Background
Before 1917, many scientists thought the universe always existed. But Einstein’s revolutionary
theory of gravity changed all the rules. It opened up the mind-boggling possibility that space itself—
the permanence of which had never been questioned—might actually be expanding. If space is
expanding, the universe we inhabit today could once have been infinitely smaller.
In 1929, astronomer Edwin Hubble made the amazing discovery that distant galaxies are
speeding away from us. This means that the galaxies we see today were once much closer
together—originating from a tiny region of space.
The origin of the universe remains one of the greatest questions in science. Current scientific
evidence supports the Big Bang model, which states that 12 to 15 billion years ago, the entire
universe began expanding from a very hot, very dense state. This sudden expansion is known
as the Big Bang.
What does it mean to say the universe is expanding? The Big Bang was an expansion of space
itself. Every part of space participated in it. Space is not simply emptiness; it’s a real, stretchable,
flexible thing. Galaxies are moving away from us because space is expanding. Galaxies are
moving with space, not through space!* The models in this activity demonstrate how the
motions of the galaxies reveal the continuing expansion of the universe.
In the 1920s, Edwin Hubble measured the motion of galaxies. By measuring a galaxy’s distance
from us and how fast that galaxy is receding (its recession velocity), he found a simple relationship:
double the distance, double the velocity; triple the distance, triple the velocity. This is
Hubble’s Law. In equation form, it is written:
v = H x d
Recession velocity = Hubble’s constant x distance from us
The slope of the graph of distance vs. velocity represents the Hubble Constant for the universe.
The Hubble Constant describes how fast the universe is expanding. By measuring the rate of
expansion, the size and age of the universe can be calculated. Interpreting recent observational
results from space-borne and ground-based telescopes, scientists have determined different
values of Hubble’s constant. Determining the precise value of the Hubble constant is key to
understanding the origin of the universe, and there are several factors that affect this determination.
For example, the universe may not have been expanding at the same rate throughout
time; that is, the expansion itself may be accelerating. Questions like these make the age of
the universe a hot topic—one of the most controversial in the study of cosmology. The age of
the universe is currently estimated to be between 12 and 15 billion years.
* There is also a local motion through space as galaxies interact
with their neighbors, but on larger scales, the expansion of
space dominates.
Suggestions for Introducing the Activity
Gather students’ ideas and questions about the Big Bang. What caused the Big Bang? Was
there anything before the Big Bang? What evidence do we have of the Big Bang? When we say
the universe is expanding, what exactly is expanding? Students should also discuss models and
the inherent flaws of any model.
In this activity, students will be using rulers to measure distances between hypothetical
galaxies and using these distances to calculate the velocities of these galaxies. Astronomers
do not have rulers in space, but the relationship between distance and velocity means that
they can calculate distances by measuring velocities. Astronomers measure the recession
velocities by looking at the spectra of the galaxies. This idea is explored further in Evidence
for the Expanding Universe.
Part 1. Elastic band model–a one-dimensional model
Materials
• Six-foot length of one inch (or greater) wide elastic ribbon, or exercise band
or bungee cord
• approximately 1/2-inch round stickers
• stapler
• tape measure
• white board or chalk board
Procedure
• Prepare the model of the universe. Stickers represent galaxies in space. The elastic band
represents space.
• Start from the center and place the stickers evenly along the elastic at approximately
one-inch intervals. Staple the stickers to keep them from slipping.
• Ask two students to each take an end of the elastic and hold it taut without stretching
against the board. On the board, mark the points of the stickers.
• Label one sticker Galaxy A.
• To model the universe expanding, hold Galaxy A still and gradually pull on both ends of
the elastic.
• Observe what happens to the distance between the galaxies.
• Measure the distance between the galaxies.
• Now choose a new sticker and label it as Galaxy B. Repeat the process, holding
Galaxy B still.
Discussion Notes
Are the galaxies moving away from each other? Is there a center to the expanding universe?
Are the galaxies themselves expanding? Is there any pattern to how far apart the galaxies
appear to be?
This model shows how galaxies farther away from us appear to be moving faster. That is, the
galaxies farthest from the reference galaxy move a greater distance in the same amount of
time. Because velocity equals distance divided by time, a larger distance over a constant time
corresponds to a higher velocity.
Part 2. Galaxy fields–a two-dimensional model
Materials
• Student Worksheet Galaxy Field A Transparency
• Student Worksheet Galaxy Field B Transparency
• Overhead projector
• transparency markers
• ruler
Cosmic Questions Educator’s Guide40
Modeling the Expanding Universe 41
Procedure
• Project Student Worksheet Galaxy Field A Transparency for everyone to observe. This is
a picture of an imaginary field of galaxies taken at one moment in time.
• Lay Student Worksheet Galaxy Field B Transparency over A. Imagine this represents the
same galaxy field one second later. Choose one galaxy (it is easier to choose a large dot)
and match up Worksheets A and B. It is important to keep the Worksheets square and
not rotate either one, as you do this.
• What can you observe about how the other galaxies appear to have moved? (It should
look as if all the galaxies are moving away from this point).
• Now choose a different point on Worksheet B to align with Worksheet A. Observe the
pattern again. (It should look again as if everything is moving away from this point.)
Discussion Notes
Are we at the center of the universe? Is there a center? Is there an edge? In the universe every
galaxy is moving away from every other galaxy. There is no center. From the point of view of
any galaxy, that galaxy appears to be the center of the expansion. This observation is similar
to observations made by a person in a moving car. Objects outside the car may appear to be
moving away, but the person inside the car does not experience the sensation of movement.
Part 3. Measuring the relative motion of galaxies
In this model the imaginary galaxy fields on Student Worksheets Labeled Galaxy Fields 1 and 2
show only a few galaxies. Students will measure the distance the galaxies appear to have
moved in one second.
Materials
Each student, or small group of students, should have:
• Student Worksheet Labeled Galaxy Field 1
• Student Worksheet Labeled Galaxy Field 2, copied onto transparency
• Expanding Universe Student Worksheet
• transparency marker
• ruler
Procedure
• Each student chooses a different galaxy and locates it in the galaxy field on Student
Worksheet Labeled Galaxy Field 1. Remember, this is just an idealized map. Real galaxies
are neither sized this regularly nor spread this regularly throughout the universe.
• Lay Worksheet 2 over Worksheet 1 and align the two using the letter of your galaxy.
This simulates one second of universal galaxy motion. Your galaxy should not appear to
have moved from the top sheet to the bottom sheet.
• What can you observe about how the other galaxies appear to have moved?
• Use a transparency marker to draw an arrow from each galaxy’s position at time
00:00:00 to where it has moved one second later. Record your observations and graph
your data on the Expanding Universe Student Worksheet.
• Collect all the copies of the Worksheet 2 transparencies. Pile the transparencies on top
of each other. You should notice that students have drawn arrows in different directions
for the same galaxy. Is it possible for something to move at different speeds and direction
at the same time? Is one set of data right and another wrong?
Discussion Notes
Each student’s galaxy seems to be the center of the expansion. The only way this could possibly
happen is if space itself is expanding because otherwise an object (such as the Sun or the
Earth) would have to be moving in two directions at once. The expansion of space is the only
way to reconcile the observation that from Earth everything appears to move away from us.
Astronomers assume that we are not in a special place in the universe; that our place in the
universe is not different from other places. This assumption is called the Cosmological
Principle. It suggests that every other place should observe the expansion just as we do—a
situation that would be true if space itself were expanding between the galaxies.
Cosmic Questions Educator’s Guide42
STUDENT WORKSHEET Galaxy Field A
Modeling the Expanding Universe 43
STUDENT WORKSHEET Galaxy Field B
Cosmic Questions Educator’s Guide44
STUDENT WORKSHEET Labeled Galaxy Field 1
Modeling the Expanding Universe 45
STUDENT WORKSHEET Labeled Galaxy Field 2
Cosmic Questions Educator’s Guide46
Choose a galaxy on Labeled Galaxy Field 1. Remember, this is just an idealized map. Real galaxies are neither this regularly sized
nor spread regularly throughout the universe.
Lay Labeled Galaxy Field 2 Transparency over Labeled Galaxy Field 1 and align the letters of your galaxy. This simulates one second
of universal galaxy motion. Align your galaxy so it does not appear to move from the top sheet to the bottom sheet. (Be careful
not to rotate the papers.)
What can you observe about how the other galaxies appear to have moved?
What direction are the galaxies moving?
Have all the galaxies moved the same distance?
Using a colored transparency marker, draw arrows on Worksheet 2 to represent the motion of the other galaxies. The arrow
should start at the center of each galaxy on Worksheet 1 and end at the center of that same galaxy on Worksheet 2. The arrows
represent the direction and speed, or velocity, of motion of the galaxies throughout the universe.
Record how the length and direction of the galactic arrows change with their position relative to your galaxy.
Graph the relationship between the distance of each galaxy from your chosen galaxy and the length of each arrow.
STUDENT WORKSHEET Expanding Universe
Distance from your chosen galaxy (cm.)
Length of arrow (cm.)
Evidence for the Expanding Universe 47
EVIDENCE FOR THE EXPANDING UNIVERSE*
Exhibit Connections: Cosmic Calendar, The Big Bang, Spectra Interactive
Goals
• to become familiar with emission spectra as sources of information
• to use galactic spectra to determine galactic speed
Materials
Each student or small group of students needs a set of student worksheets:
• Looking at Spectra
• Calculating and Graphing Galactic Speed
• Images of Four Galaxies
• Spectra of Galaxies A, B, C, and D
Students should have access to color images of all spectra, including those on the Student
Worksheet Looking at Spectra.
Background
The previous activity helps students to visualize a universe expanding in all directions. In this
activity, students use astronomical evidence to explore this notion further. How do we know
the universe is expanding?
The Big Bang model of the origin of the universe states that the universe originated in a very
hot, very dense state 12 to15 billion years ago and has been expanding and cooling ever since.
There are three lines of evidence that support this model.
1. We observe that galaxies are moving away from us.
2. We can detect the afterglow from this hot dense state of the early universe. The hot
glowing fog that once filled all of space has now cooled to an “invisible” sea of lowenergy
microwaves (in the radio region of the electromagnetic spectrum). Telescopes sensitive
to microwave light detect this afterglow across the entire sky and show that we are
bathed in this radiation that dates from when the universe was barely 300,000 years old.
3. Spectroscopic observation of the universe shows its chemical composition to be roughly
75% hydrogen, 25% helium by mass (12 to 1 ratio of hydrogen to helium atoms). The
creation of so much helium from hydrogen in nuclear reactions could only have happened
if the universe was at some point in time very hot and very dense.
In this activity students examine the first line of evidence, galactic motion. Galaxies are so
large, and so far away, that you could never see them move just by looking – even if you
looked for a whole lifetime through the most powerful telescope! However, there is a way
to detect the motion of a galaxy. By examining the spectrum of light from a galaxy, you can
determine whether the galaxy is moving toward or away from us, and how fast. Students will
look at optical images of four galaxies. They will then compare the emission spectra from
these same four galaxies and measure the wavelength of the red hydrogen line for each galaxy.
Because of the Doppler effect, the wavelength will shift as the source travels through space.
Suggestions for Introducing the Activity
Students should already be familiar with the electromagnetic spectrum and understand that
atoms emit and absorb light of fixed standard wavelengths. In Part 2, students observe the redshift
of the hydrogen lines in the spectra of galaxies. You may wish to introduce the concept of
Doppler shift before completing this activity, or use the activity to motivate a discussion about
the relationship between motion and wavelength. For an online tutorial about the Doppler effect,
visit cfa-www.harvard.edu/seuforum/galSpeed or www.pbs.org/wgbh/nova/universe/moving.html.
* This is adapted from an online activity: How Fast Do Galaxies Move? An
Interactive Lab. Produced for NASA’s Office of Space Science by the Smithsonian
Astrophysical Observatory © 2001 Smithsonian Institution. It can be found at:
http://cfa-www.harvard.edu/seuforum/galSpeed
Part 1. Looking at Spectra
Atoms emit and absorb light of fixed, standard wavelengths. An emission or absorption spectrum
shows a specific pattern of lines that is a kind of “fingerprint,” unique to the particular
types of molecules. The emission spectrum of glowing hydrogen gas has one bright red line,
a fainter blue line, and several other faint lines. The red line for hydrogen has a wavelength
of 656 nanometers.
A spectrum of a galaxy is the pattern produced when the light from the galaxy is passed
through a prism or similar device. The element hydrogen is the most common element in
the universe, and it is plentiful in galaxies. Hydrogen is present in huge clouds of gas that
fill some of the space between the stars in a galaxy. The bright red hydrogen line is an easily
recognizable feature in many astronomical spectra.
Procedure
• Observe the spectrum of the Sun on the Student Worksheet.
• Observe the spectrum of the fluorescent lamp on the Student Worksheet. Have
students record the colors they see and the wavelengths.
• Observe the spectrum of hydrogen gas. Have students record the colors they see and
the wavelengths.
• Look again at the spectrum of the Sun and look for dark lines at these recorded wavelengths.
Although these absorption lines are not as dramatic as the emission lines in
the pure hydrogen spectrum, their presence tells us that the Sun contains hydrogen,
and that this hydrogen is absorbing light.
• Observe the spectrum of the sample galaxy on the Student Worksheet. Determine the
wavelength of the red hydrogen line in this spectrum. Note that the position of this
peak is different from the laboratory sample of hydrogen.
• Discuss why the red hydrogen line would be in a different place.
Part 2. Analyzing Galactic Spectra, Calculating and Graphing Galactic Speed
As students observe the emission spectra from four different galaxies, they will observe that in
each spectrum the bright red hydrogen line has shifted from its characteristic wavelength of
656 nanometers, as seen in the laboratory spectrum of hydrogen gas. This shift toward the
longer wavelength part of the spectrum, which is the redder end of the spectrum, is called
“redshift.”
The observed redshift can be used to calculate the galaxy’s velocity. The amount of the
observed redshift is proportional to the speed of the source (for speeds that are not close to
the speed of light). For example, light from a galaxy moving away from us at 10% of the speed
of light will be redshifted by 10%. The hydrogen line that was at 656 nanometers will be redshifted
by about 65 nanometers to 721 nanometers. (As speeds approach the speed of light,
the principles of relativity must be used to explain the relationship between an object’s redshift
and its speed. However, the speeds of the galaxies in this activity are much less than the
speed of light, so the simple proportion described above can be used.)
Using the galactic spectra, students will calculate how fast Galaxies A, B, C, and D are receding
from us, and graph that in relation to the galaxy’s estimated distance from us.
Cosmic Questions Educator’s Guide48
Evidence for the Expanding Universe 49
Procedure
• Give each student or small group of students optical images of the four galaxies, A, B,
C, and D.
• Tell students to assume that these four galaxies are all approximately the same actual size.
• Ask students to arrange the four galaxies in order of distance from the earth. Discuss
what evidence they used for their choices.
• Label the graph on the student worksheet by writing the letters of the galaxies in order
of their estimated distance along the x- axis.
• Give each student or small group of students the spectra of the four galaxies, A, B, C,
and D.
• Determine the wavelength of the red hydrogen line in the spectra from galaxies, A, B, C
and D. Record these on the worksheet.
• Compare the wavelength of the red hydrogen line in each galactic spectrum to the laboratory
sample of hydrogen gas. By how much has the line been shifted? What fraction of
the original wavelength is it? At what fraction of the speed of light is the galaxy moving?
• Calculate the recession velocity of the four galaxies using the Student Worksheet.
• Plot the velocity data on the y-axis of the graph on the Student Worksheet.
Discussion Notes
In the 1920s, Edwin Hubble measured redshifts to determine the velocities of galaxies. He
found that there was a linear relationship between a galaxy’s distance from us and how fast
that galaxy is receding (its recession velocity). This simple relationship can be described in
equation form, where the slope of the graph of distance vs. velocity represents the Hubble
Constant for the universe.
v = H x d
Recession velocity = Hubble’s constant x distance from us
This equation, known as Hubble’s Law, states that a galaxy at double the distance will have
double the velocity; at triple the distance, it will have triple the velocity. Hubble’s Law is
important in understanding the age and size of the universe, and is described further in the
background information for the previous activity, Modeling the Expanding Universe.
Suggested Answers
These notes provide answers to some of the questions on the Student Worksheets and can be
used to help guide a class discussion.
In Part 1, when looking at the pure hydrogen spectrum, students should measure peaks at
656 nanometers, 486 nanometers, and 434 nanometers. Although this third line is not visible
in the color image, it can be measured on the graph. All three of these lines appear in the
spectrum of the Sun and may be easier to find in the graph than in the color image.
In Part 2, we have assumed all the galaxies are all the same actual size. Therefore, Galaxy B,
which appears largest in the optical image, is presumed to be closest to us. Accordingly, the
smallest image (C) is farthest away. In order from closest to farthest, the galaxies are B, D, A,
and then C.
Cosmic Questions Educator’s Guide50
Galaxy Distance vs. Speed
0
12,000
24,000
36,000
48,000
B D A C
(fastest)
Speed of
galaxy
(slowest)
(closest) (farthest)
Distance from us
(km/s)
Galaxy B is about 210 Mly (million light years) from the Milky Way.
Spectrum B shows the hydrogen line at 666 nanometers. This is redshifted 10 nanometers, or
1.5 %, from its original location of 656 nanometers. Therefore, the velocity of Galaxy B is 0.015
times the speed of light (300,000 km/s), which equals about 4,500 km/s. Students may measure
the redshift to be between 5 and 13 nanometers, which corresponds to a recession velocity
between 4,350km/s and 6,000 km/s.
Astronomers calculate the recession velocity of Galaxy B to be 4350 km/s.
Galaxy D is about 750 Mly from the Milky Way.
Spectrum D shows the hydrogen line at 690 nanometers. This is redshifted 34 nanometers, or
5 %, from its original location of 656 nanometers. Therefore, the velocity of Galaxy D is 0.05
times the speed of light (300,000 km/s), which equals about 15,000 km/s. Students may measure
the redshift to be between 29 and 39 nanometers, which corresponds to a recession velocity
between 13,000 km/s and 18,000 km/s.
Astronomers calculate the recession velocity of Galaxy D to be 15,400 km/s.
Galaxy A is about 1,520 Mly from the Milky Way.
Spectrum A shows the hydrogen line at 724 nanometers. This is redshifted 68 nanometers,
or 10 %, from its original location of 656 nanometers. Therefore, the velocity of Galaxy A is 0.10
times the speed of light (300,000 km/s), which equals about 30,000 km/s. Students may measure
the redshift to be between 65 and 73 nanometers, which corresponds to a recession velocity
between 29,000 km/s and 34,000 km/s.
Astronomers calculate the recession velocity of Galaxy A to be 31,400 km/s.
Galaxy C is about 2,260 Mly from the Milky Way.
Spectrum C shows the hydrogen line at 752 nanometers. This is redshifted 96 nanometers, or
15 %, from its original location of 656 nanometers. Therefore, the velocity of Galaxy C is 0.15
times the speed of light (300,000 km/s), which equals about 45,000 km/s. Students may measure
the redshift to be between 94 and 102 nanometers, which corresponds to a recession
velocity between 42,000 km/s and 47,000 km/s.
Astronomers calculate the recession velocity of Galaxy C to be 44,700 km/s.
Sample Graph
Evidence for the Expanding Universe 51
The Sun
STUDENT WORKSHEET Looking at Spectra
This is the spectrum of the Sun.The pattern is created by passing light from the Sun through a glass prism, which separates
the light into its component colors. In addition to the familiar rainbow of colors, notice the dark lines.These lines are
produced by atoms in the Sun’s atmosphere that absorb certain wavelengths of light.This dark-line pattern is called an
absorption spectrum. Note that the pattern extends past the red, into the infrared region. Infrared light is not visible to our
eyes. It is colored grey in this image.The grey area to the left of the blue is part of the ultraviolet region of the spectrum.
Fluorescent Lamp
This is the spectrum of a Fluorescent Lamp. Instead of a complete rainbow, we see only certain colors of light.This bright-line
pattern is called an emission spectrum. We don’t see a full rainbow because rainbows are produced only by light sources that
are very hot.
What colors do you see in the Fluorescent Lamp spectrum, and what are their wavelengths?
Cosmic Questions Educator’s Guide52
STUDENT WORKSHEET Looking at Spectra (continued)
This is the spectrum of a galaxy.The pattern was produced when the light from this distant galaxy was passed through a
device similar to a prism. In addition to the rainbow, there is a bright red line.This line comes from the element hydrogen.
Determine the wavelength of the red hydrogen line in the spectrum of the sample galaxy.The peak has been shifted from its
characteristic wavelength (as measured above in the hydrogen spectrum) toward the longer wavelength part of the spectrum,
which is the redder end of the spectrum.This phenomenon is called a “redshift.”
In the sample galaxy, the red hydrogen peak is at ___________________ nanometers.
This is the emission spectrum of the element hydrogen. Hydrogen is the simplest chemical element.The pattern was produced
by taking the light from a glowing tube of hydrogen gas, and passing the light through a prism.
What colors do you see in the hydrogen spectrum, and what are their wavelengths?
Look for lines at these same wavelengths in the spectrum of the Sun. Which lines can you see?
Sample Galaxy
Hydrogen Gas
Evidence for the Expanding Universe 53
Look at the optical images of the four galaxies A, B, C, and D. These galaxies, are all approximately the same actual size.
Which galaxy do you think is closest to us? Farthest?
_________ _________ _________ _________
Closest farthest
What evidence did you use in these choices?
Label the x-axis of the graph on page 2 with the letter of the galaxies, in order from closest to farthest.
Look at the spectra of the four galaxies A, B, C, and D. Determine the wavelength of the red hydrogen line in each spectra.
Galaxy A: _____________ nanometers Galaxy B: _____________ nanometers
Galaxy C: _____________ nanometers Galaxy D: _____________ nanometers
The observed redshift is proportional to the speed of the source (for speeds that are not close to the speed of light). For
example, for a galaxy moving away from us at 10% of the speed of light, the light will be redshifted by 10%. The hydrogen
line that was at 656 nanometers in the laboratory sample of hydrogen gas will be redshifted by about 65 nanometers, and
will be observed at 721 nanometers.
By how much has the red hydrogen line been shifted in the spectra of galaxies A, B, C, and D? What fraction of the original
wavelength is this? At what fraction of the speed of light is the galaxy moving?
Galaxy A: redshifted ____ nanometers =____ % Galaxy B redshifted ____ nanometers =____ %
Galaxy C: redshifted ____ nanometers =____ % Galaxy D redshifted ____ nanometers =____ %
Calculate the speed of each galaxy as it is receding from us, using the percentages from your answer above. The speed of
light is approximately 300,000 kilometers per second (186,000 miles per second).
Galaxy A: ____ % x 300,000 km/s = ________ Galaxy B: ____ % x 300,000 km/s = ________
Galaxy C: ____ % x 300,000 km/s = ________ Galaxy D: ____ % x 300,000 km/s = ________
STUDENT WORKSHEET Calculating and Graphing Galactic Speed
Plot the speeds of Galaxies A, B, C and D on the y-axis of the graph.
What can you conclude about the relationship between galaxy distance and redshift?
How does this evidence support the theory of an expanding universe?
Cosmic Questions Educator’s Guide54
STUDENT WORKSHEET Calculating and Graphing Galactic Speed (continued)
Speed of
galaxy
(km/s)
Galaxy Distance vs. Speed
0
(fastest)
(slowest)
(closest) (farthest)
Distance from us
Evidence for the Expanding Universe 55
Galaxy A Galaxy B
Galaxy C Galaxy D
STUDENT WORKSHEET Images of Four Galaxies
Cosmic Questions Educator’s Guide56
Evidence for the Expanding Universe 57
Spectrum of Galaxy A
Spectrum of Galaxy B
STUDENT WORKSHEET Spectra of Galaxies A and B
Galaxy data courtesy of Emilio Falco, Center for Astrophysics
Cosmic Questions Educator’s Guide58
STUDENT WORKSHEET Spectra of Galaxies C and D
Spectrum of Galaxy C
Spectrum of Galaxy D
IsThere Life on Other Worlds?The Drake Equation 59
IS THERE LIFE ON OTHER WORLDS? THE DRAKE EQUATION*
Exhibit Connections: Welcome Home, Are We Alone?
Goals
• to estimate the number of worlds in the Milky Way galaxy that have life
• to think about the size and composition of the galaxy and how it affects the possibility
of extraterrestrial life
• to understand and estimate the terms of the Drake Equation
Materials
• Student Worksheets (one set per student or small group of students)
• calculators
Background
Are we alone? For the first time in history, astronomers have discovered planets orbiting stars
beyond our own Sun. In fact, planetary systems seem to be widespread in the universe. Is there
life, intelligent or otherwise, in any of these alien solar systems? No one yet knows. But ours may
be the first generation to detect a sign of life beyond Earth. What will it mean if we find out that
we are not alone?
At first, “Is there life on other worlds?” seems a simple question to answer. However, it quickly
becomes a complex web of issues. What is life, anyway? How does it begin and evolve? What
conditions can life tolerate? What makes a planet habitable? How do we look for and identify
extraterrestrial life? To attempt to resolve these kinds of questions, astrobiologists draw on
many branches of science and employ many research strategies, such as fieldwork, laboratory
research, telescopic observation, and exploration with spacecraft.
Though we have not found any examples of extraterrestrial life, comparisons with certain
kinds of life on Earth suggest that potential habitats for extraterrestrial life, and maybe life
itself, do indeed exist. However, contrary to popular notions, if extraterrestrial life is found
in our solar system, it will most likely be bacteria-like.
In 1961, the astronomer Dr. Frank Drake suggested an organized framework for thinking about
life in the galaxy. Known as the Drake Equation, it provides a way to estimate the number of
worlds within our Milky Way galaxy that have intelligent life and whose radio transmissions
should be detectable. Drake identified a sequence of eight terms to help people think about
what must occur before a world can be inhabited by a civilization with radio technology. This
activity uses Dr. Drake’s framework to have students consider the implications of each term
and make their own estimates of life in the Milky Way galaxy.
Because we are unsure whether there is life out there, let alone intelligent life with which we
can communicate, there is no correct solution to the equation—the value of each factor is
open to interpretation.
* Adapted from Life on Earth…and Elsewhere. Astrobiology in your classroom.
Educator Resource Guide. Developed by the NASA Astrobiology Institute (NAI),
with funds from the NAI LeadTeams at NASA Ames Research Center and NASA
Jet Propulsion Laboratory, andTERC’s Astrobiology Curriculum Project. Fall 2000.
Suggestions for Introducing the Activity
The Drake Equation is an experiment in estimation, similar to something called a Fermi
problem, in which a set of constraints is applied to figure out an unknown quantity. For
example, to figure out how many people in a certain city drive blue minivans, you would
start with a known quantity, such as the number of people in the city and then apply the
following constraints:
What percentage of those people have driver’s licenses?
What percentage of those people have families?
What percentage of those families need minivans?
How many car companies make minivans?
What percentage of those minivans are blue?
And so on, until you reach an answer.
You may wish to set up your own Fermi problem to get the students thinking about estimation
in this way.
To get a sense of what your students think when they hear the term “extraterrestrial,”
ask them: What is the chance we are the only life in the universe? Are there such things as
extraterrestrials?
Procedure
• Discuss and define the word extraterrestrial. A broad meaning includes anything from
microbes to plants to intelligent creatures.
• Identify factors related to the existence of extraterrestrial life. Ask students what information
they would need to determine the probability of extraterrestrial life. You might
begin by saying, “Let’s see if we can estimate how many worlds out there have life (or
intelligent life with which we can communicate). What would we need to know?”
Record the ideas.
• Introduce the Drake Equation as one scientist’s effort to identify the factors in the same
way students did. Have students complete the Student Worksheet Is There Life on
Other Worlds and estimate values for each term. Make sure they understand that there
are no right answers. The Drake Equation simply helps us think about the factors
involved in determining the probability of communicating with civilizations that have
radio technology.
• After making estimates for each term, have students multiply the eight terms and
determine their estimate of the number of other civilizations that exist in our Milky
Way galaxy that we can detect using radio technology (Question 1 on the Student
Worksheet Is There Life on Earth. . . and Elsewhere?).
• Have students report their estimates and discuss the range of values and their
implications.
• Use the Student Worksheet Is There Life on Earth. . . and Elsewhere? to guide a class
discussion.
REMEMBER: Most, though not all, of the terms on the Student Worksheet are given as percentages,
rather than numbers. Students should be careful in their calculations.
Cosmic Questions Educator’s Guide60
IsThere Life on Other Worlds? The Drake Equation 61
Discussion Notes
These notes provide answers to some of the questions on the Student Worksheet Life on
Earth…and Elsewhere? and can be used to help guide a class discussion based on those
questions. Questions 2, 3, 7, 8, 9, and 11 ask students to reflect on their own feelings, perceptions,
or idea, and therefore have no background notes.
1. Based on the eight terms, what is your estimate?
While terms 5 through 8 are percentages, the final number that students obtain is a discrete
number rather than a percentage or a probability. This number represents a student’s estimate
of the number of civilizations with radio technology that we can detect.
4. What if your answer to Question 1 were less than one?
Some scientists think that the likelihood of life arising elsewhere in the galaxy is very remote,
while others surmise that life should be quite plentiful. An answer less than one would imply
that the chances for life in the galaxy are very small, and the fact that we do have life on one
planet, Earth, means that the chance for life on any other planet is nearly impossibly small.
So an answer less than one is not “wrong”; it instead implies that Earth is something of an
amazing, one-of-a-kind fluke. If students choose low probabilities for terms 5 through 8, they
may come up with a number less than one. For students to increase their answer to greater
than one, they may need more than the 400 billion stars in the Milky Way galaxy. One way to
do this, without changing any of their estimates, would be to add another term (see discussion
notes for Question 14), such as multiplying their answer by the number of known galaxies to
see how many inhabited planets would be in the whole universe, instead of just the Milky Way.
5. In which terms did you have the most or least confidence?
Estimating numbers for the eight terms becomes increasingly a matter of conjecture as one
goes from term 1 to term 8. There is widespread agreement only for the first two terms.
6. Are you more optimistic or conservative?
An answer of one states that Earth is the only place with intelligent life that has radio
technology. There may still be life or even intelligent extraterrestrials out there, but we cannot
communicate with them because they do not have radio technology. Any number larger than
one implies that we may receive signals from intelligent extraterrestrials someday. However,
make the distinction between detection and communication, which is a two-way exchange.
With a small final number, actual communication is less likely. With a large final number,
actual communication becomes increasingly likely.
10. What are the implications of discovering microbial life?
Many students express disinterest in discovering anything less than a bona fide, Hollywood-style
extraterrestrial. However, no life beyond Earth has ever been found, which implies that life may
be a rare accident that happened on Earth due to an extraordinary convergence of circumstances
and that it is unlikely to happen elsewhere. In this context, discovering microbial life
would help us understand more about how life arises and what conditions it can tolerate.
Furthermore, it would help answer the question of whether life is a common process in the
universe. In short, discovering microbial life beyond Earth would be a profound discovery.
By multiplying terms 1 through 5, students can make their own estimate of how many worlds
in our galaxy have life of any sort.
12. What is the most abundant life form on Earth?
We live in the age of bacteria. For the past three and one half billion years, bacteria have been
the dominant life form in terms of numbers and biomass. They are key to many biological, geological,
and chemical processes, and many scientists think that multi-cellular organisms became
possible only after single-celled bacteria began living symbiotically within a cell membrane.
13. If life exists elsewhere, what do you think it will look like?
Astrobiologists feel that most extraterrestrial life will be bacteria-like, living beneath a planet’s
surface and using chemical energy for their needs. Animal life, and especially intelligent animal
life, is probably much rarer.
14. Can you think of any other terms that might affect your estimation of life in the universe?
As mentioned in the discussion notes for Question 1, this equation only addresses life in
the Milky Way galaxy. The universe is made up of many galaxies, perhaps an infinite number.
Multiplying your estimate by the number of galaxies in the universe, would increase the possibility
of life beyond Earth. Remember, however, that the time required for a signal to reach us
from another galaxy is much longer than the time required from within our own galaxy. Other
factors, such as the inclusion of habitable moons in a planetary system, may also affect the
probability of detecting extraterrestrial life.
Student Extension: Exploring the already discovered planets
When the Drake Equation was first developed, scientists only had evidence for the first two
criteria. Today, astronomers are able to detect planetary systems around other stars. What we
know about solar systems within our galaxy is changing every day, and each new piece of
information helps us refine the details of detecting extraterrestrial life. When the Cosmic
Questions exhibit was created, there were more than 80 planets detected outside our solar system.
By the time this activity guide was published, the number was more than 100. The search
continues even today, not just for extra-solar planets, but for planets that might contain life.
Visit planetquest.jpl.nasa.gov to learn more about the ongoing search for life beyond Earth.
NASA’s Planet Quest website, planetquest.jpl.nasa.gov contains an atlas of currently known extrasolar
planets. Students may wish to explore this website and learn more about specific planetary systems.
Cosmic Questions Educator’s Guide62
IsThere Life on Other Worlds?The Drake Equation 63
STUDENT WORKSHEET Is There Life on Other Worlds?
Using the Drake Equation
Background
These numbers are based on observations of the stars in
our galaxy, the Milky Way galaxy, and of other galaxies we
believe to be like our own. Most scientists believe the
number of stars to be 400 billion.
Many scientists believe that a star has to be like our Sun.
Only about 5% of the stars in our galaxy are sun-like stars,
though about 10% are closely related, either slightly
warmer or slightly cooler. About 50% of stars exist in binary
or multiple systems, which many scientists feel make them
inappropriate.
Appropriate stars may not have planets circling them. We
have only just begun detecting extra-solar planets, so we
don’t really know how common they are.
Our only example of this term is our own solar system.
Could Earth be the only habitable place in our solar
system? Is our system typical? Remember that if one
system has no habitable planets and another has four,
the average would be two per system.
Having a planet that is appropriate for life doesn’t
necessarily mean that life will arise. No real data are
available to help us estimate this term. Earth is the only
planet on which we know there is life. However, bacterial
life existed on Earth shortly (geologically speaking) after
its formation, possibly indicating that the development of
life is easy. Many scientists believe that whether or not
life arises depends on many factors.
On Earth, humans developed intelligence, apparently as an
evolutionary advantage. However, this term depends on
how you define intelligence. Are dolphins, gorillas, octopus,
and ants intelligent? Furthermore, single-celled life existed
on Earth very early, and multicellular life took 2.5 billion
years to form (a very long time, geologically speaking).
Maybe the development of complex life, let alone intelligent
life, is unusual.
Communication with intelligent extraterrestrials requires
that we hear from them. Given the vast distances of space,
they would probably send signals that travel at the speed of
light, such as radio waves. On Earth, humans have only just
developed radio technology, so possibly this term should
have a low value. But, we did eventually develop radio
technology, so maybe this is true of all intelligent beings.
Will an extraterrestrial’s signals overlap with the lifespan of
the receiving civilization? Extraterrestrials that sent signals
a hundred thousand years ago from a world a hundred
thousand light years away would still overlap with us, even
if they died out long ago. So, how long do civilizations with
radio technology last? A high level of technological development
could bring with it conditions that ultimately
threaten the species. Or maybe, once a society has radio
technology, it may survive for a long time. Finally, radio
signals may give way to more advanced, less noisy
technologies such as lasers. No one would hear us then!
Term
1. The total number
of stars in the
Milky Way galaxy
2. The percentage
of stars that are
appropriate
3. The average number
of planets
around each
appropriate star
4. The percentage of
planets within a
solar system that
are habitable
5. The percentage of
habitable planets
that develop life
6. The percentage of
planets with life
that develop
intelligent life
7. The percentage of
intelligent life
that develops
radio technology
8. The percentage
of "current"
civilizations
having radio
technologies
Conservative
Estimate
100 billion
5%
1
10%
On average,
there is one
habitable planet
in every 10
systems
0.000001%
Life is a rare
accident that
is unlikely to
happen
elsewhere
0.0001%
or less
Only one in a
million planets
with life will
develop
intelligent life
0.0001 or less
Only one in
1,000,000 planets
with intelligent
civilizations will
develop radio
technology
0.0001%
or less
One in a million
civilizations with
radio technology
will develop it in
time to detect
signals from
another
civilization
Optimistic
Estimate
600 billion
45%
10
50%
Half the
planets in
every system
are habitable
100%
Life will arise if
conditions are
appropriate
100%
Any planet
with life will
develop
intelligent life
100%
All intelligent
life will
develop
radio
technology
10%
One in a ten
civilizations
with radio
technology
will develop it
in time to
detect signals
from another
civilization
Your
Estimate
Remember to convert percentages to numbers!
1. To find out your estimate of the number of worlds in the Milky Way galaxy that have intelligent life that we can detect using radio technology,
fill out the Student Worksheet Is There Life on Other Worlds? Using the Drake Equation. Multiply the eight terms. Don’t forget
to convert percentages to numbers. Write your final answer here:
2. Based on your estimates, how good are our chances of hearing from intelligent extraterrestrials?
3. How does your answer to Question 2 compare with what you thought before you began the activity?
4. What if your answer to Question 1 were less than one? What would that mean in terms of our existence here on Earth?
5 . When making estimates, in which terms did you have the most confidence? The least? Why?
6 . Are you more optimistic or conservative when it comes to thinking about extraterrestrial life with radio technology in the Milky Way
galaxy? Why?
7. How could you adjust the estimates in the equation to have it come out so that Earth is the only planet in the Milky Way galaxy with
radio technology?
8 . If tomorrow’s newspaper headline read, “Message Received from Outer Space,” what would it mean to you?
9 . What would your reaction be if we discovered microbes on another planet? Plants? Insects? Mammals? Intelligent life?
10. If microbial life were discovered on another planet, what implications might such a discovery have?
11. How would you define extraterrestrial now? How does your current definition differ from the one that the class developed earlier in
the activity?
12. What do you think is the most abundant life form on Earth?
13. If life exists elsewhere, what do you think it will look like?
14. Can you think of any other terms that might affect your estimation of life in the universe?
Cosmic Questions Educator’s Guide64
STUDENT WORKSHEET Life on Earth. . . and Elsewhere?
IsThere Life OutThere? Community Survey 65
IS THERE LIFE OUT THERE? COMMUNITY SURVEY
Exhibit Connections: Welcome Home, Are We Alone?
Goal
• to survey other people to find out their thoughts about life beyond Earth and compare
their ideas with visitors to the Cosmic Questions exhibit
Materials
Survey Questions
calculators
Background
Visitors to the Cosmic Questions exhibit have the opportunity to complete the following survey.
Students can conduct their own survey before or after a visit to the exhibit and compare their
answers to exhibit visitors. Students could also see whether there is any variation or pattern in
answers from men and women or people of different ages. To do this, students will need to
design their own method for tracking demographic data.
Procedure
• Have students survey other people in the school, their family, friends or community
members. Each student should ask many different people.
• Compile the data from the entire class.
• Calculate the percentage of people who gave each response.
Discussion Notes
How do your responses compare with the general visitors to the exhibit? Are the responses
similar or different? How might you explain the results?
Compare your answers to visitors to the Cosmic Questions exhibit while it was at the Museum of
Science in Boston from September to December of 2002.
1. Do you think there’s life out there in the universe? Percentage of people who
chose this response
No. We’re all there is. 9
Maybe some forms of life. 37
Yes. Intelligent life. 31
Lots of intelligent life. 23
2. When do you think we’ll find signs of life beyond Earth?
In the next 10 years. 9
In my lifetime. 28
In 100 years. 36
In 1,000 years or more. 27
3. How would you feel if life were discovered tomorrow?
A bit frightened. 22
Thoughtful. 29
Really glad. 26
We’ll see. 23
4. What’s the simplest form of life you would find exciting?
Chemical signs of life. 20
Bacteria or lower plants. 33
Slimy or furry things. 23
Only intelligent life. 24
Cosmic Questions Educator’s Guide66
IsThere Life OutThere? Community Survey 67
Survey people in your school, family or community using the following multiple choice questions. Each person should
choose one response for each question. Record their responses.
1. Do you think there’s life out there in the universe?
Tally Total
No. We’re all there is.
Maybe some forms of life.
Yes. Intelligent life.
Lots of intelligent life.
2. When do you think we’ll find signs of life beyond Earth?
Tally Total
In the next 10 years.
In my lifetime.
In 100 years.
In 1,000 years or more.
3. How would you feel if life were discovered tomorrow?
Tally Total
A bit frightened.
Thoughtful.
Really glad.
We’ll see.
4. What’s the simplest form of life you would find exciting?
Tally Total
Chemical signs of life.
Bacteria or lower plants.
Slimy or furry things.
Only intelligent life.
Total number of people surveyed: ___________
STUDENT WORKSHEET Is There Life Out There? Community Survey
Cosmic Questions Educator’s Guide68
Visiting the Cosmic Questions Exhibit 69
VISITING THE COSMIC QUESTIONS EXHIBIT
These are some suggestions of things students can do during a visit to the exhibit.
• Watch the Cosmic Kitchen Theater presentation and experience the “recipe” to create
the universe.
> Write a synopsis of the presentation for someone who has not seen the exhibit.
> At the end of the story Sophie (a character in the story) says, “Hey wait…I have so
many questions!” And she asks her Dad, “What do you think came before the Big
Bang? Do you think the universe will ever end? Do you believe there are people on
other planets, or cows or apple pie?” How would you answer Sophie’s questions?
What are your questions?
• Find two new models of astronomical phenomena, such as objects, concepts or events,
in the exhibit.
> What physical features of the real thing do they represent?
> What physical features do they not represent?
• Visit the Control Your Own Telescope exhibit and request an image to be sent to your
email address.
> Record what you request.
> Print this image at home or school and bring it to class.
• Visit the cosmic poetry wall.
> Create your own poem.
> Copy it down to share with other students in your class.
• Watch part of the Humans Muse video.
> Pick one of the questions and express your opinion about it.
• Think of your own cosmic questions.
> Visit http://image.gsfc.nasa.gov/poetry/ask/askmag.html to see if your questions have
been answered or to submit your question to a scientist.
• Conduct Cosmic Questions Partner Interviews using the Worksheet on the
following pages.
Cosmic Questions Educator’s Guide70
Your Cosmic Questions 71
YOUR COSMIC QUESTIONS
Partner Interviews
Exhibit Connections: All displays
Goals
• to focus your ideas and work with a partner to learn more about the universe
• to think critically about the Cosmic Questions exhibit
Materials
Student Worksheet
Background
Cosmic Questions: Our Place in Space and Time was created to initiate a cosmic conversation
with visitors about the universe. The exhibit explores three fundamental questions—What
is the universe like? Was there a beginning to time? How do we fit in?—but many more
questions are addressed throughout the displays and activities. Use this activity to formulate
and focus your own cosmic questions as you investigate the exhibit.
Procedure
• Divide the students into pairs.
• Questions 1 and 2 should be completed before visiting the exhibit.
• Questions 3 through 6 should be completed in the exhibit hall.
Cosmic Questions Educator’s Guide72
Your Name: _________________________________________________
Your Partner’s Name: __________________________________________
Answer Question 1 before visiting the exhibit.
1. What questions do you have about the beginning of the universe?
Your questions:
2. Interview your partner about his or her cosmic questions.
Your partner’s questions:
Spend some time exploring the exhibit.
3. What question(s) from the exhibit did you find most compelling?
Your question(s):
4. Interview your partner about the questions in the exhibit he or she found most compelling.
Your partner’s questions(s):
5. Choose an exhibit station to address one of the questions above. Which station did you choose? What does it ask the
visitor to do? What do you think the designer of this exhibit component wants the visitor to learn? What would you
change about this exhibit station to better address your question?
6. Interview your partner and describe the station that he or she visited.
STUDENT WORKSHEET Your Cosmic Questions
RESOURCES
Cosmic Questions Homepage
Find out more at http://cosmicquestions.org
Our Place in Space
Universe! Education Forum: http://cfa-www.harvard.edu/seuforum
This site, hosted by the Smithsonian Astrophysical Observatory, contains information and
educational activities related to NASA’s space science research into the structure and
evolution of the universe.
Imagine the Universe: http://imagine.gsfc.nasa.gov
Astrophysicists at NASA’s Goddard Space Flight Center offer “a glimpse into the mysteries of
our universe . . . what we know about it, how it’s evolving, and the kinds of objects it contains.”
Powers of Ten: http://powersof10.com
From the folks who created this famous film of the same name, this site offers an introduction to
size and scale in the universe.
Welcome to the Universe: http://www.mos.org/sln/wtu/index.html
The Museum of Science, Boston created this site as an introduction to learning about our
place in space.
Observing the Universe, Learning from Light
Multi-Wavelength Astronomy: http://www.ipac.caltech.edu/Outreach/Multiwave/
NASA’s infrared data center at Caltech hosts this site full of multi-wavelength images
and information.
Chandra X-ray Observatory: http://chandra.harvard.edu
Chandra’s website includes an extensive photo album with multi-wavelength images.
Our Place inTime
MAP Homepage—information about cosmology and the Big Bang:
http://map.gsfc.nasa.gov/
NASA’s MAP probe is studying the microwave light left over from the early universe.
An Ancient Universe—How Astronomers Know the Vast Scale of Cosmic Time:
http://www.astrosociety.org/education/publications/tnl/56/
This article from the American Astronomical Society and the Astronomical Society of the Pacific
presents the evidence for an ancient universe.
Great Cosmic Mysteries
Planet Quest: http://planetquest.jpl.nasa.gov
This NASA website presents the latest data on extrasolar planets.
Black Holes and Beyond: http://archive.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoles.html
This website contains information about theory and existence of black holes in our universe.
General Astronomy Resources
Space Science Education Resource Directory: http://www.TeachSpaceScience.org
A searchable database of NASA space science activities and resources.
Astronomy Picture of the Day: http://antwrp.gsfc.nasa.gov/apod/astropix.html
A gallery of astronomical photographs and images.
Resources 73
Cosmic Questions Educator’s Guide74
Funded by
Cosmic
Questions
Our place in space and time