Download 1. The Birth of a Star

Figure 1- Our Sun as a Red Giant star, swollen near its doomed planet, Earth
A Celestia Educational Activity
The Life and Death of Stars
version 6
rev 4, September, 2004
Celestia Educational Activity 6 – The Life and Death of Stars
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Table of Contents
The Life and Death of Stars
(click on any title below to go there)
Background Information .............................................................................................................................3
Introduction ...................................................................................................................................................4
In the Heart of the Milky Way ....................................................................................................................5
1. The Birth of a Star - The Nebula Stage ..............................................................................................7
2. The Protostar Stage ............................................................................................................................10
3. The Main Sequence or Yellow Supergiant Stage ...........................................................................12
3a. Brown Dwarfs – failed stars .............................................................................................................15
4. The Red Giant and Supergiant Stage ..............................................................................................15
5. The Death of Earth (and the inner planets) .....................................................................................18
6. A new Beginning on Pluto? ................................................................................................................20
7. The Death of a Red Giant Star – the Planetary Nebula stage .....................................................20
8. The White Dwarf and Black Dwarf Stages.......................................................................................22
9. The Death of Large Stars – Supernova Stage ................................................................................23
10. The Death of Large Stars - Neutron Star and Pulsar Stage .......................................................25
11. The Death of Large Stars - The Black Hole ..................................................................................27
12. Conclusion ..........................................................................................................................................28
13. Credits: ................................................................................................................................................29
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Background Information
This is a Celestia educational activity. It will take you on a special journey through space and time, to
examine the birth, life and death of stars. Along the way, you will encounter some of the most amazing
objects in the universe, including Black Holes, Red Giants and Pulsars. You will also discover the fate of
Earth. Celestia activities are designed for middle and high school students in grades 7 to 12, but can be
used by anyone who wishes to explore our universe. This activity employs the use of a visually stunning
space simulation program named Celestia. Celestia runs on most computers but does require your
computer to have the following minimum capabilities:
1. A CPU speed of at least 800 MHz
2. An operating system running Windows 98, ME, 2000, NT, XP, or MAC OSX
3. RAM memory of at least 128 MB (256 – 512 MB preferred)
4. A video graphics card with at least 32 megabytes of RAM (64 – 128 MB recommended)
5. OpenGL graphics rendering capability
If you are not sure if your computer has these things, we suggest you download Celestia and try it out.
During this activity, you will be asked to use certain buttons and menu controls within Celestia. If you
are unfamiliar with the program, don’t worry. We will guide you step-by-step through your journey.
Celestia is provided to you absolutely free of charge for use with this activity. If you are within a school,
your computer may already have Celestia loaded on it. Ask your teacher. If it is not there or if you are
working from home, you must download Celestia.
To do so, visit our website at
http://www.shatters.net/celestia/download.html and locate the version of Celestia that best matches your
computer’s operating system. Once downloaded, left-click on it twice (double-click) and it will install
itself on your computer (Windows systems) or install the program as your MAC OX, Linux or Unix
system instructs you. After it installs, return to this document to begin our Celestia journey together.
If you are using this activity in school, your teacher will tell you how to arrange your computer screen so
that you can both read this open document and use Celestia. If you are doing this activity from home, we
suggest you read it on screen while also viewing and using Celestia, by offsetting the two “windows” so
that the top of both windows is always visible. A shortcut way of switching views is simply to press
the [Alt] and [Tab] keys on the keyboard at the same time (Windows systems). Press them again to
switch views back.
A student worksheet is provided as a separate document (Activity 6 worksheet). You may want to keep
that worksheet handy for filling in information as you discover it. Your teacher may ask you to fill in this
document for a grade.
Celestia was created and is generously provided to you free of charge by Chris Laurel and the Celestia
Open Source group and is available to everyone on the internet at www.shatters.net/celestia. We
encourage you to visit the site. If you wish to explore this great program in more depth, we urge you to
download the Celestia User’s Guide, Part 1 from that site. It will teach you how to use every control and
feature of the program.
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Introduction
When Celestia opens, press the [V] key to turn off all text visible on the screen. Then, dim the room
lights if possible. Block out all external distractions and just contemplate the view in front of you for at
least a minute. Press the [6 →] key or [4 ←] key to slowly rotate your view around completely. Take
your time. Not many people on Earth get to observe the incredible beauty of space from your vantage
point.
If you’ve had an opportunity to take the journey titled, “Celestia Educational Activity 1 and 2 – the
Universe”, you have discovered that the depths of space are almost infinite in size and stretch to limits
almost beyond our capability to imagine. Populating that dark cold space are the stars, newly estimated in
number at over 140 sextillion (140,000,000,000,000,000,000,000). If you added up all the grains of sand
on all the beaches and at the bottom of all the oceans on Earth, you would not have enough grains to
represent the stars we believe exist in the Universe. Incredible but true!
Celestia is displaying only a tiny portion of
the stars in our nearby neighborhood, the
amount your eyes might pick up looking into
space without a telescope. However, hidden
in that darkness are billions more stars, too
dim or far away to see with just our eyes. To
see more of them, press and hold down the
{ ] } key on your keyboard. WOW!
The stars you see before you are part of a
much, much bigger group. Stars exist in
space as enormous collections of stars called
Galaxies. A Galaxy contains many billions
of stars, held together by the force of gravity.
ALL stars occur only in galaxies. Between
the stars is mostly empty space but there are
Figure 2 – a representation of a galaxy not too far from our own
Milky Way galaxy. Each tiny white dot is a star. The colored
material is nebula gas and dust. The bright yellow glowing blob
in the center is a huge concentration of stars, billions of them
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places where huge thin clouds of gas and dust collect. The gas is mainly Hydrogen (H), with some traces
of Helium (He) and Lithium (Li). The dust represents small pieces of all of the other 90 elements that
make up the Periodic Table of the natural elements. These include Carbon (C), Oxygen (O), Nitrogen
(N), Calcium (Ca), Iron (Fe) and yes, even Gold (Au).
Since all stars exist only in galaxies,
that means our own Sun and the stars
you see in your viewscreen are part of
a galaxy of stars. Our galaxy’s name
is the Milky Way. We are one of
over 200 billion stars in our Milky
Way.
Location of
our Sun
Figure 3 – An artist’s sketch of our own Milky
Way. Our Sun is approximately positioned
where the arrow points.
We can see the Milky Way with our
own eyes by simply looking up at
night. Every star in the sky is part of it. On a dark night, far from city lights, the densest region of the
Milky Way is a hazy band of whitish matter that looks a bit like a faint cloud in space. In your
viewscreen, it is crossing the center of the screen and is where the highest concentration of stars exists.
That white stuff is actually stars … billions of stars … clustered so close together that their light merges
into a broad milky haze. Mixed in with the stars is also gas and dust … countless trillions and trillions of
tons of it. How all those stars, gas and dust got there, and what will become of them over time, is the
journey of discovery you are about to take.
Through the magic of Celestia, we are going to take you to the birthing grounds of stars and explain how
they form. We will then lead you through their life story, and end with their deaths. Yes, stars are born
and eventually, they die. Yet as you will learn, their deaths can lead to new re-births, of new stars and
possibly of planets suitable for the development of life. In fact, you exist on Earth because some stars
died in this part of space long ago. The atoms that make up your body actually came from stars that blew
up and died billions of years ago.
Note: For ease of use, we suggest you arrange this document and Celestia together on the same screen in
a “tiled” fashion, so that you can see the borders of both of them. To switch from the document to
Celestia and back again, just click once on the border. Alternatively, you can press the [Alt & Tab] keys
at the same time. In Windows® systems, this will switch from document to program and back again.
In the Heart of the Milky Way
1. Let’s turn off some of the stars. Press the [V] key to turn back on your screen’s text display. Then,
repeatedly press the { [ } key so that your text display says the “Magnitude limit” is between 9.7 and
9.9. The number of stars you see will return to a typical view as seen in space with our eyes only.
2. You are in a very special and very fast spaceship. Its name is the Celestia 2. It is one of just two such
ships that have been built for use in the Celestia universe. You may have already ridden on the
Celestia 1 in a prior Celestia adventure.
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3. Would you like to see the Celestia 2? You can, by launching an external camera. To do so, click here
once only (it is important to click only once) to activate the camera. The camera will take position off
the starboard (right) side of your beautiful ship. She looks fast, doesn’t she? To get a better look,
point onto the Celestia viewscreen with your mouse, press/click the right mouse button and while
holding it down, drag the mouse. Your view will turn around the ship. This right-click-drag action
will be used a lot, so remember it. Examine your ship from all sides.
4. Then, turn off the camera and return to the inside of your ship by clicking here once. You will be
looking through your front view window, with the Sun reflecting off your ship’s metallic nose. The
ship’s internal lights are off so you can see better. Your ship’s powerful engines are also off at the
moment. It is quiet now and your ship is silent. Outside the ship, it is in fact, totally quiet. In space,
there is no air or atmosphere. Sound requires something to pass through. If there is no air, sounds
cannot be heard. It is also incredibly cold outside your ship’s hull. The temperature of deep space is
more than -400° F (-240°C) below zero.
5. Lets’ review your ship’s HUD text displays. In the upper right corner, you will see today’s Date and
Time display. The date is shown as (year, month, day). The time is in the format (hours, minutes,
seconds Universal Time or local time) on a 24-hour clock. For example, 2003 06 18 01:33:33 UTC
means you are viewing the sky as it looks in the year 2003 on June (the 6th month) 18 (the 18th day) at
about 1:33 (and 33 seconds) AM, Universal Time (UTC). Universal time is commonly used by
Astronomers and the military. Alternatively, your time may be set to your local time zone.
6. Under the date and time display are the words, “Time stopped.” That means that everything on the
screen is stopped at the moment. Of course, time stops for no one, but in Celestia, it is sometimes
helpful to be able to pause time to give you an opportunity to read these instructions. To resume Real
time, return to Celestia and locate and press the [\] key now.
7. In space, stars and planets are very large and take a lot of time to move (rotate or travel). Since we do
not have a lot of time, we may wish to speed time up on occasion. To do so, return to Celestia and on
the keyboard, type the letter [L]. The display in the upper right corner will change to read, “10x
faster. Type [L] again and it becomes 100x faster. Hit [L] again and the time clock speeds up again.
To slow time down, type the letter [K]. To return quickly to Real time, press the [\] key again.
8. In the upper left of your ship’s display will be the word, “Celestia 2”. This advises you that your
ship’s navigation computer is locked onto your own ship. In a few moments, we will begin our
journey and command the Celestia 2 to lock onto another object. Once it does so, that object’s name
will appear in the upper left corner instead.
9. In the lower left corner is your ship’s speed. You are stopped now so your speed is 0.000 m/s (meters
per second). Later, we will be accelerating to very high speeds and this display will change.
10. What are stars? Where do they come from? How do they form? How long do they exist? Do they
end? If so, what happens to them? These are very good questions. For most of our history, we
simply didn’t know these answers. Of course, many people took a guess, but in most cases, it turned
out to be wrong.
11. Beginning in the 16th Century, things began to change. Thinkers and inventors in Europe like
Copernicus, Brahe, Galileo, Kepler, Cassini and Newton began to develop telescopes, tools and ideas
that for the first time, gave us a new window into the blackness of space. They began a long process
of discovery that continues today as the modern science of Astronomy. Literally hundreds of
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thousands of men and women worldwide now study space in detail and entire government agencies
such as the National Aeronautics and Space Administration (NASA) and the European Space Agency
(ESA) are devoted to space science. These men and women have invented powerful telescopes, and
have launched hundreds of satellites into space that enable us to see far into the cosmos, detecting
minute details of galaxies, stars and planets. Through these tools, we have made great progress in
unraveling the mystery of where stars come from, how they form, and what kind of life cycles they
undergo. Let’s begin our story by firing up our swift spacecraft and traveling to a nursery … where
new stars are being born! Are you ready?
1. The Birth of a Star - The Nebula Stage
12. To position your ship for the trip, click here once. The Milky Way and Sun will be visible in your
ship’s window. Your ship is far from Earth, drifting near the outer planets of our Solar System. Now,
press the [C] key once. This will instruct your ship to swing and point its nose (the bow) directly
toward a faint colored cloud in space named “M42”. Notice that in the same info display, the distance
from you to that cloud is listed as 1,177.7 ly. The “ly” stands for “Light Year”. It is not a time, but a
distance. It is the distance a beam of light will travel through space in one year.
13. Light travels faster than any other thing in the entire universe. Its speed is an incredible 186,000
miles/sec (300,000 km/sec) and is abbreviated “c”. Nothing else travels that fast … no spaceship or
asteroid or moving star … nothing even comes close. That speed is so fast that you could travel
completely around the Earth 7 times every second. In a year moving at that speed, light will travel 5.9
trillion miles (9.5 trillion km). In scientific notation terms, a light year is 5.9 x 1012 miles, or 9.5 x
1012 km. Notice that M42 is over 1,177 light years away. That means that if you could travel in a
ship at the incredible speed of light toward that distant cloud you see before you, it would still take
you 1,177 YEARS to get there (provided we ignore a bizarre principle of Physics known as the Time
Dilation Effect of Special Relativity). The span of space between you and M42 is ENORMOUS.
14. Fortunately, the Celestia 2 is a “special” ship. It can travel faster than the speed of light. We won’t
have to wait 1,177 years to make our first stop in the story of a star’s life cycle.
15. M42 is a cloud of gas and dust in space called a “Nebula”. It really is in the night sky where you see
it, and it does look like this, but your eyes are too small to see it clearly without a telescope.
However, on a clear night, you may be able to make out its dim outline, if your know where to look.
To help orient you, locate and press the [/] key. This will turn on the outlines of the constellations.
Constellations are patterns of stars in the sky that some folks think look like something familiar. M42
is called the “Orion Nebula” because it is located within the famous constellation of Orion, the
Hunter. Orion is visible on most dark nights in the Northern Hemisphere during the autumn and
winter months. Look for the 3 bright stars that cross the hunter’s belt. Notice where M42, the Orion
Nebula is in relation to the constellation of Orion. It is below the belt of stars. When done, press the
[/] key again to turn off constellation outlines.
16. To begin our trip, press the [F] key once. This will command your ship’s computer to lock onto M42
and “follow” it. A display in the lower right corner of your screen will now say, “Follow M42”.
17. Now, let’s fire up Celestia 2’s powerful engines. To do so, press the [A] key on the keyboard. You
will begin moving forward slowly through space. Your speed will be listed in the lower left corner of
the screen. You will begin moving at a very slow speed, measured in meters per second (m/s), but as
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you continue tapping the [A] key, your speed will increase. Soon, you will be moving at thousands of
meters/sec (km/s), then at fractions of the speed of light (abbreviated c) per second. If you go too fast,
press the [Z] key. This slows you down. Remember these commands; A to speed up, Z to slow
down. To stop your ship completely, press the [S] key.
18. Let’s accelerate to a speed far in excess of the speed of light (c). To reach it quickly, press the [ F 7 ]
function key at the very top of the keyboard. This is a shortcut command to the Celestia 2’s engines
to accelerate to the impossible speed of one light year per second (1.000 ly/s). This is over
30,000,000 (30 million) times faster than the speed of light. Yet even at this speed, it will still take us
1,177 seconds (about 19 minutes) to reach M42. Let’s shorten that journey even more. Tap the [A]
key several times more to accelerate from 1 ly/s to between 8 and 9 ly/s. Now, your flight to M42
will take only a few minutes. Sit back and enjoy it. Stars will begin passing by on both sides. Watch
your Distance display in the upper left corner. When you get between 40 and 30 ly of M42, press the
[S] key on the keyboard. This turns off your engines and also brings your ship to a quick stop.
19. What you are looking at is the birthplace
of stars, a nursery that is helping to create
and nurture stars. It was created here a
long time ago, when gases and atoms of
elements drifting in space between the
stars began to gather and collect by the
force of gravity. Gravity can be thought
of as a powerful attractive force that all
objects and matter have. It comes from
all atoms that exist in the universe. Even
the atoms in your body are giving off a
gravitational force that is pulling on
Figure 4 - M42, the
things around you.
It makes no
Orion Nebula
difference what the object is ... a
computer, TV, person, rock, tree or star.
Everything attracts everything else by gravity. Gravity also works over very long distances.
Although it gets weaker as distances between objects increase, it never really disappears entirely.
Your body for example, is giving off a gravitational force that is pulling on the Earth and moon, on
the Sun itself and on every star you can see in the sky. It is even pulling on M42 before you.
Likewise, the Earth and moon, Sun and stars and M42 are all pulling on you with their own
gravitational forces. Because the Earth is so large and so close to you, its gravitational force is the
most powerful around you and pulls you down to the ground. You stay put here on Earth.
20. What if we took you off the Earth, however, and put you far away in space, far from other stars. That
is where the Orion nebula is. Out here, exist mostly gases and small particles of many other elements
in nature. About 90% of all the visible mass in the universe is the simplest element, Hydrogen. All
star-forming nebula are made mostly of it. Second in concentration is Helium (a bit less than 10%).
The small percentage left consists of traces of “dust” made of such elements as nitrogen, oxygen,
carbon, lithium, iron and even gold and silver. In fact, all 90 natural elements that exist in nature can
be found in space in differing trace amounts. They all drift around in thin clumps of gas and dust.
21. Over time (a LOT of time), that gas and dust will be attracted to each other through the force of
gravity. Over millions of years, gravity will pull a wisp of gas here and a grain of dust there together
until it collects as a big cloud of material, a fog gathered into a large clump in space we call a Nebula.
M42, the Orion Nebula in front of you is one such cloud. Actually, it is two clouds. Notice that on
its right side, a second purplish nebula has formed. It is called NGC 1977, and is similar to M42.
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22. How is M42 and NGC 1977 a birthplace for stars? The answer is simple. Stars are made of the
material you see in front of you. M42 contains the “food” that feeds a new star. Its concentrated
clump of mostly hydrogen gas plus some elemental dust contains the starting material … the nutrients
that nurture the growth and development of a new star.
23. Notice a bright part of M42 near the top right corner? That is a new
“star” developing, slowly gathering matter from the Nebula around
it through the force of gravity. It is not yet a true star but it is
growing every day, getting hotter and bigger. Someday, it will
become a full-fledged star. Lets’ move toward it. Our control needs
to be tight here. We don’t want to fly into the Nebula.
24. Before we approach it, you will need to learn how to steer your ship.
Figure 5 – a new star forming
On the number keyboard on the right side of your keyboard, locate
in M42
the [8↑], [2↓], [4←] and [→ 6] keys. Do you see them? There
should be a small light on above those numbers, labeled Num Lock. If the light is not on, press the
key that says [Num Lock] so that the light comes on.
25. Then, return to Celestia and tap the [8↑] key. Your view of M42 will move (pitch) downward. The
[2↓] key pitches your view upward. Tap the [4←] key. Your view will move to the left. Tap the
[→ 6] key and your view will move to the right. The [7] key and [9] keys rotate your view. Practice
with these keys for a minute, until you are comfortable with what they do. You will use them often.
When you are ready, click here.
26. Press and hold down the [A] key and accelerate to a speed of about 0.2 to 0.3 ly/s. Slowly, the Orion
Nebula will enlarge. Steer toward the bright region in figure 5 above, using your steering keys. When
you are within about 7 light years (7 LY) on the Distance display, press [S] to stop your ship. Now,
swing your view around using the six steering keys and enjoy a view no human has ever actually seen
in real life; a closeup of M42 from only 7 light years out. What a beautiful nursery! All stars,
including our Sun, started out in a place like this; a giant Nebula cloud of Hydrogen gas and elemental
dust which gathered by gravity in the cold of space.
27. Celestia has several beautiful star nursery nebulae to show you. Your ship is programmed to take you
to a second one. To visit one of the most active, click here. You will be taken to the Rosette Nebula,
a massive nebula that is giving birth to hundreds of stars. To take a short tour, press the [ F 7 ] key.
Your hyperdrive engines will come on, and you will begin moving toward the nebula at the incredible
speed of 1 ly/sec. Use your steering keys and fly through the stars in the Nebula for a minute or two.
Enjoy the beauty of these young stars, some just born, some teenagers. Remember the size of this
nebula. These stars in front of you are trillions of miles apart from each other, and the Rosette Nebula
is hundreds of light years wide. Press the [S] key to stop your ship when done exploring.
28. Our next stop is one of the most beautiful birthing places in the Milky Way. It is called the Eagle
Nebula. To go there, click here. What a striking place! Press the [F7] key and fly toward it for a bit.
Turn and explore for a minute or so. Press [S] when done. The nebula gases and dust in front of you
represent so many colors because they are particularly rich in different elements. In fact, all 90
elements from the Periodic Table are dense here. The stars that are forming in the Eagle will have
dense solar systems of planets, developing from all that nebula material. How planets form is part of
the next chapter in our story of the life of a star.
29. If part of a class lesson, go to the worksheet you’ve been provided and complete the questions prior to
and including Nebula. Go to Worksheet.
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2. The Protostar Stage
30. What is going to happen to the many bright glowing regions of gas that you see in front of you? Over
many thousands of years, the force of gravity will pull different clumps of them tighter and tighter
together, pulling the gases and heavy elements toward their centers. Repeated in different regions
throughout the nebula, atoms will bang and collide in space and the core of these regions will heat up
hotter and hotter from the friction of atoms rubbing, banging and crushing together. Eventually, these
hot clumps will exceed a million degrees and still they will get hotter, and denser. One by one, the
gases will glow with heat much brighter than you see them now.
31. Nebula clouds, and regions of dense clumping within nebula clouds, will also begin to spin. Due to
the way atoms come together in space by gravity, most very young stars begin to spin as they collect
nebula gases and dust. Let’s journey to two such young stars, still in the process of forming. To
enjoy our view, press the [V] key until no text appears on the screen.
32. To position you for the first journey, click here. The Celestia 2 will depart the Eagle Nebula and fly
you at hyperspeed to a section of the Rosette Nebula that has begun to pull together by gravity into a
new star, and has begun rotating. This is the beginning of step 2 in a star’s life cycle, called the
“Protostar” stage.
33. To fly into the heart of the rotating nebula/protostar, press the [F6] key. Your engines will come on at
an impossible speed of 1 au/s. Steer with your steering keys as outlined earlier. Dip toward the
nebula and fly/skim along its top. Pass the central protostar, fly across to the other side of the nebula
and turn around with your [4←] and [→ 6] keys. Notice that this new star is part of the Rosette
nebula which you visited a few minutes ago. That is how almost all stars form. Gravity collects a
small clump of gas and dust of a much bigger nebula into a protostar. When done exploring, press [S]
to stop your ship.
34.
Over time, this baby protostar will
develop further. Gravity will pull it
tighter and it will begin to glow very hot.
Let’s visit a star that has reached a later
stage in Protostar development. It is also
part of the Rosette nebula. To go there,
click here. Your ship’s NAV computer
will steer your ship to a most amazing
object. It is almost formed. Gravity has
pulled it into a tight glowing ball.
Surrounding it is part of the nebula that it
formed from, captured by its gravity and
spinning also.
Figure 6 – a Protostar with nebula, rotating and growing
35. You may be wondering about those two amazing “jets” which are coming out the top and bottom of
the protostar. They are part of the nebula gas, forced to “squirt” out, guided by the electrical and
magnetic forces that are being generated inside the rotating star. Over time, the jets will disappear,
but for thousands of years, they will be there, spraying energetic high speed atoms of gas away from
the young star. Most young protostars have them.
36. The reddish colored “disk” of gas and dust that is spinning around the protostar has a special role to
play in the life cycle of this star. Do you notice that some areas of the nebula are thicker and denser
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than others? That disk is full of both gas and dust containing heavy elements such as iron and silicon,
calcium, aluminum and carbon. Slowly, gravity is forcing the thicker, denser regions of that spinning
disk to clump also. Little whirlpools of very dense material are forming where these clumps are
thickest … and from that material … you guessed it … planets and moons are growing. Spread out
before you is not only a new star in the making, but an entire solar system, not yet fully developed but
soon to be so. How long will the wait be? Due to its enormous size, this new solar system may take
millions of years to fully develop, but someday in the future, a complete system of planets and moons
surrounding this hot young star will be here.
37. In fact, there are already two or three new planets present. To visit one, click here. Your ship will
move to a position off the hot protostar. Look closely in front of the star, at the rotating nebula. Can
you see a small dot moving, imbedded in the nebula? Wait until it passes by the front of the star, then
press the [F] key. Your ship will lock onto it and follow it.
Figure 7 – a hot new planet
38. Now, press the [G] key and your rocket
engines will come on and take you
automatically to this new protoplanet. It
has no name yet. It is simply called “B”. It
is hot and still semi-molten. Lava is
flowing freely across its surface as space
dust and rocks continue to rain down on it,
smashing into it and causing it to grow
bigger and denser. Currently, it is smaller
than Earth but year by year, “B” is
enlarging and maturing. Press the [L] key
once to slow down time a bit and witness
this baby planet rotating for a minute.
Right-click-drag around it a bit. WOW!
39. Billions of years ago, our solar system formed this way, and our Earth looked much like this young
planet. Celestia Educational Activity 9 is the story of the Primitive Earth and Moon system, at a
time long ago when both were young, hot and violent. Look for it on our website.
Celestia Educational Activity 9
The Primitive Earth and Moon
Examines how we think the Moon/Earth system formed.
It is under development. You can find it at
http://www.fsgregs.org/celestia, or at the Celestia add-on
repository at http://www.celestiamotherlode.net
40. Let’s get really close to this hot new protostar. To do so, click here. The Celestia 2 will take you
close to the central hot core, but not too close. Enjoy the view. This protostar is hot and glowing. It’s
internal core temperature is well over 4 million degrees C and climbing. Its surface temperature is
close to 6,000° C. Yet, its heat comes primarily from friction and gravitational compression of its
atoms. It has not yet grown up to become a full star. That is the next stage in our journey.
41. Go to the worksheet and complete the questions on Protostars. Go to Worksheet.
Celestia Educational Activity 6 – The Life and Death of Stars
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3. The Main Sequence or Yellow Supergiant Stage
42. Deep within the protostar, something is happening. As the gravity of the star pulls more and more
nebula material onto it, pressing down and crushing it denser and denser, its central core is being
compressed to incredible pressures. This compression forces its atoms to rub and crush together. The
result is an increase in temperature. The core will get hotter and hotter. It will exceed 4 million
degrees C and still it will climb. Year after year, century after century, it will get hotter.
43. The material in new stars being formed today is primarily hydrogen gas (about 75%), helium gas
(about 24%) and 1% of everything else on the periodic table. Hydrogen is a simple substance with an
atomic mass of 1. In atomic terms, hydrogen is just a single proton surrounded by one buzzing
electron.
44. When the temperature in the core of a new star reaches in excess of 10 million° F (5.5 million° C), the
protons of hydrogen actually smash into each other with such force and energy that they begin to
FUSE. The process is called Hydrogen Fusion. Four Hydrogen protons fuse together and form a
nucleus of Helium (made of 2 protons and 2 neutrons). As you can note, two protons will change to
neutrons in the fusion process. That results in a release of LARGE amounts of energy into the core,
which migrates up to the surface of the star and escapes into space as huge bubbles of heat and gas. It
is the same process that occurs in a hydrogen bomb.
45. To see that process in action, click here once and wait for the animation to open. Left-click on the
play button (the one in the middle). You will see atoms colliding faster and faster until they begin to
fuse, while the core of the star begins to glow white-hot with radiant energy, giving off vast amounts
of heat and radiation into space.
46. In reality, stars that get hot enough in their cores to begin fusing hydrogen to helium actually begin
blowing up, exploding like a bomb. However, gravity, which has pulled all that material together in
the first place, prevents these hydrogen fusion explosions from destroying the star. Instead, the star
swells from the explosions to a particular size and stabilizes there. It is exploding outward and is
being pulled back by gravity inward at the same time. A balance occurs … called fusion equilibrium.
Figure 8 - a star undergoing nuclear
fusion explodes outward and is pulled
inward by gravity. It stabilizes in size
and is in “equilibrium.”
Celestia Educational Activity 6 – The Life and Death of Stars
47.
pg 13 of 29
When a star begins fusing
hydrogen into helium in its core,
it is now a fully grown, fully
developed star.
No more
material falls onto it because the
explosions in its core heat it up
to such a high temperature (over
20 million° F, or 11 million° C)
that hot matter from the star
begins flying off into space at
high speed, like a wind blowing
away from the star. As seen in
the prior movie, this “Solar
Wind” of hot gases moves away
from the star at over 1 million
mi/km per hour and blows away
the remaining gas and dust that
once surrounded the protostar.
Figure 9 – The solar wind from a new main sequence star blows the nebula away.
48. The new star, now actively fusing hydrogen into helium in its core, goes by several names. If it is a
star similar in size to our Sun, it is called a “Main Sequence” star. The color of such stars range from
blue-white to orange. They have enough hydrogen to burn for hundreds of millions to billions of
years. For example, our Sun is a small Main Sequence star. It is not burning hydrogen into helium as
fast as some stars, so it is a bit cooler and less energetic. It will fuse hydrogen to helium for close to
10 billion years before it runs out of hydrogen fuel in its core. It is about 4.6 billion years old now, so
it has over 5 billion years to go before hydrogen fusion stops inside its core. Most stars in the night
sky are Main Sequence stars and live for similar periods.
49. The color of a star depends upon its surface temperature. Hot stars are blue-white in color. Average
temperature stars are white to yellowish, and cooler stars are orange to pink in color. The hotter the
star, the faster it goes through its hydrogen fuel and the shorter is its lifespan.
50. Our Sun is an average to small sized star. In fact, in some Astronomy texts, it is identified as a
“yellow dwarf”. Many stars in the universe are average in size, a bit bigger than our Sun. However,
there is no reason why a star has to be average sized and in fact, more than 80% of the stars you can
see in the night sky are bigger in diameter than our Sun. If the nebula cloud from which it grows is
denser and wider than the one that formed our Sun, gravity will organize it into a larger clump. A
larger protostar will form and from it, a larger hot star will ignite.
51. Stars in their hydrogen fusion stage can in fact, grow to very large proportions and burn through their
fuel quickly. For example, stars 5 to 500 times larger than our Sun populate the night sky. Stars that
are several times larger than our Sun fuse hydrogen at a much faster rate because their mass is greater,
their core temperatures are hotter and they are exploding more violently. These stars are not only
much hotter, but they expand to a bigger size during hydrogen fusion and are called “Yellow or
White Giants”. They go through their “main sequence phase” in millions rather than billions of
years. Really BIG stars can get so hot during fusion that they turn blue-white in color, swell to
massive proportions and are called Blue Supergiants. These stars go through their fuel furiously.
They have only enough hydrogen in the core to last only 10 million years or less, even though they are
much more massive. They are very short-lived stars.
Celestia Educational Activity 6 – The Life and Death of Stars
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52. In summary, a Main Sequence star is one that has grown up and has begun fusing hydrogen into
helium in its central core, causing the star to explode with energy and heat. Gravity keeps it from
blowing itself to bits. Our Sun is a Main Sequence star. Most typical main sequence stars are white
to orange in color and will convert Hydrogen into Helium for hundreds of millions to billions of years.
53. If the star is larger than our Sun, it may develop into a Yellow, White or Blue Giant or even into a
Supergiant star that is much bigger and is burning/fusing its hydrogen so fast that it will last for only
100 million years or less.
54. The Celestia 2 is ready to take you to some of these stars. Let’s start with our own Sun. Return to
Celestia, press the [K] key and slow time back down to Real time. Next, press the [H] key (think of
Home), then press the [C] key and [F] key. Your ship will turn and lock onto the Sun, which is just a
tiny star over 5,500 light years from your current position. Press the [G] key and you will be taken at
hyperspeed to our Sun. Zoom in closer with the [Home] key and speed up time to 10000x faster with
the [L] key. To restore your HUD text display, press the [V] key once.
55. The surface of our Sun is about 10,000° F (5500° C). Its core temperature, however, is over 20
million ° F. It has been fusing hydrogen into helium for billions of years. As mentioned, it is actually
exploding, but gravity is holding its size steady. It is in equilibrium. It has enough hydrogen in its
core to continue hydrogen fusion for about 5 billion more years.
56. Although your ship is reasonably close to the Sun now, you are safe only because the Celestia 2 has a
special hull to protect you from the enormous radiation and energy pouring out of the Sun. In fact, it
is enough to warm the Earth over 93,000,000 miles (1 Astronomical Unit) away. That energy is due
to the ferocious fusion of Hydrogen occurring inside the core. As you watch, large amounts of hot gas
from the surface of the Sun are also being blasted off the star and thrown into space as the Solar Wind.
Some of it is even hitting your ship now.
57. Let’s attempt a very dangerous maneuver. Let’s try to skim over the outer atmosphere of the Sun.
You can only do so for a few moments without overloading your ship’s cooling systems. Press the
[A] key and accelerate toward the Sun at about 0.2 c. As the Sun approaches, use your arrow keys
and change course so that you just skim over the top of the Sun, passing through its yellowish
atmosphere but not plunging into its surface. Can you do it? WHEW! When done, press [S] to stop
your ship.
58. Let’s visit some stars that are larger than our Sun. Press the [B] key to turn on star labels and rightclick-drag until you locate the star named “Sirius”. Left-click on it to select it, followed by the [G]
key. Your ship will take you to a bright, large white star that is the brightest star in our sky, next to
the Sun itself. Zoom in close with the [Home] key. Press the [V] key again to turn on your
“complete” information display. Slow down time to 1000x faster with the [K] key. In the upper left
corner, you will notice that this star has a radius of 1.88 times that of the Sun (1.88Rsun). In other
words, it is almost twice as large as our Sun. Its brightness is given by the word, “Luminosity”.
Notice that it is over 24 times brighter than our Sun. It is a larger White Main Sequence star and is
burning its hydrogen fuel faster than our Sun, causing it to also be hotter (whiter) in color. It is so
bright because it is very close to our Solar System (only 8.6 ly away).
59. Next, press the [Enter] key and type “Canopus”. Press [Enter] again and [G] to go there. Zoom in
close. Canopus is a very big star 71 times larger than our Sun and 14,000 times more luminous
(bright). It is burning its Hydrogen fuel far faster than our Sun. It is currently a Yellow –White
Giant star, based upon its temperature. It will enter old age and the next stage of its life cycle long
before our Sun. When finished viewing, press the [B] key to turn off star labels.
60. To visit a truly monster star that is simply burning itself up, press [Enter], type “Rigel”, press [Enter]
again and [G] to go there. Zoom in and speed up time to 10000x faster. This Blue Supergiant star is
Celestia Educational Activity 6 – The Life and Death of Stars
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simply incredible. It is 17 times more massive, 60 times bigger in diameter and is over 40,000 times
brighter than our Sun. Its surface temperature is almost double our Sun’s surface temperature and its
internal core temperature is over 50 million °F. If a planet existed anywhere near Rigel, it would be
baked, fried and sterilized by the ferocious radiation. There would be no possibility of life on it.
Someday in the not too distant future, Rigel will explode with a gigantic force that will be felt here in
our Solar System, 42 ly away.
61. Answer the questions on Main Sequence stars. Go to Worksheet.
3a. Brown Dwarfs – failed stars
62. As you’ve just learned, nebula that are large enough will give birth to a protostar that will eventually
ignite in the fires of nuclear fusion, and burn for millions to billions of years. But what about small
nebula? After all, just because there is some gas in space does not mean a star will form. What if the
nebula is simply too thin and doesn’t have the gravitational mass to collapse a star into a density that
will start a nuclear fusion chain reaction? Are there such nebula? What happens to the protostars that
form in them?
63. The answer is interesting. The protostar gets hot and begins to glow with friction, but never reaches
fusion temperatures. It never ignites. In a way, it is an aborted star. Gravitational friction will keep it
hot and it will spin, but its glow will be just a dull red, dim and practically invisible among all the
other stars. Over millions of years, it will slowly cool and
die down until it becomes a dense “Brown Dwarf”. That
is the name Astronomers give to stars that never make it
… and fail to begin nuclear fusion. They really are
brownish red.
64. Let’s go to one. Click here and your ship will take you to
a spot in space only 2,500,000 km from a Brown Dwarf
star. The dwarf has no name, but it orbits a star called 61
Figure 10 – a Brown dwarf
Cyg B. Zoom in close and right-click-drag around it.
You are in front on a failed star that began as a companion
to 61 Cyg B and 61 Cyg A (nearby), but which failed to capture enough nebula material to form more
than a small protostar … not enough to ignite into fusion. It glows now only dimly as gravitational
compression keeps it modestly hot from friction alone.
65. Answer a few questions on Brown Dwarfs. Go to Worksheet.
4. The Red Giant and Supergiant Stage
66. All main sequence and giant fusion stars live long lives by fusing hydrogen in their cores into helium.
However, all things come to an end. At some point, they run out of hydrogen fuel near the core.
There is still plenty of hydrogen gas in a thick ring around the outside regions of the star, but it is far
too cool to fuse into helium. The fires of nuclear fusion finally die down in the core region and the
star, which has been exploding for millions or billions of years, calms down. The explosions that
have been trying to blow the star up fade away. Now, gravity, which is always present, seizes the
Celestia Educational Activity 6 – The Life and Death of Stars
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star’s mass and begins pulling it again toward the center. The diameter of the star shrinks rapidly and
the core is crushed again by enormous gravitational pressures. Day by day, week by week, the mass
of the star tightens and presses down on the core. Week by week, the temperature rises from the
pressures. It exceeds 50 million degrees and still continues to get hotter. Month by month, the now
old, burned out Main Sequence or Yellow Giant star gets smaller and internally hotter.
67. Finally, as it collapses, the temperatures in the core region begin to exceed the incredible temperature
of 100 million degrees. At that point, two things happen:
68. A) The leftover hydrogen that is still outside the core but close to it gets hot enough to resume fusing
furiously into helium in a large “ring” of burning hydrogen fusion surrounding the core. The
ring expands outward and “pushes” the star to begin swelling in size/diameter.
69. B) The helium nuclei that make up the core of the star become so hot that they also begin FUSING
HELIUM into Carbon, Oxygen and Neon. Helium fusion is more energetic than Hydrogen
fusion and releases more energy.
70. The star stops collapsing. Instead, it now blows up again, expanding and swelling away from its core
in enormous explosions, but this time, there are two sources of explosion, the hydrogen fusion
explosions going on in a ring around the core, and the helium fusion explosions occurring in the core.
The star rapidly swells outward to 100 - 200 times its original size and more. It becomes a truly
GIANT star. However, gravity is still powerful enough a force to keep the star from blowing itself to
bits. It settles into a new size and a new equilibrium, much, much larger than before, but still holding
together.
71. In fact, the surface of the star, the only part we see, is so far away from the heat generating fusion
zone and core (millions of miles/km), that it cools off significantly and becomes red in color, rather
than hot white or yellow. The visible star becomes a RED GIANT or SUPERGIANT.
72. Our Sun is facing this fate. Calculations reveal that our Sun will swell to a Red Giant about 5 billion
years from now.
Figure 11 – Our Sun below, will become a Red Giant someday
Hydrogen fusion
region
Our Sun now
Helium
fusion
Celestia Educational Activity 6 – The Life and Death of Stars
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73. What happens if the star is already large; that is, if it starts out as a Yellow, White or Blue Giant? The
answer is that when it runs out of hydrogen, it undergoes the same process as a smaller Main
Sequence star. It contracts, heats up and again explodes with both hydrogen and helium fusion
occurring. However, it is so large a star and is so hot, that it becomes a GIGANTIC Red
Supergiant.
Some of these massive stars can reach a diameter over 1,000 times that of our Sun.
74. Would you like to visit a few of these giants? We can fly the Celestia 2 to do so, but we have to be
careful. The radiation is stupendous near these Red Giant and Supergiant stars. We can’t linger long.
75. Return to Celestia, press [H] to select Home, and [G] to go there. We will return to our Solar System.
Next, press [Enter] and type the word, “Betelgeuse”. Press [Enter] again, then [C] to center it in
your viewscreen. A modestly bright reddish star will be centered. Press the [/] to temporarily turn on
constellation borders, and you should discover
that Betelgeuse is the top, Orion the hunter
reddish star of the constellation “”. Press the
[/] to temporarily turn off borders.
76. Betelgeuse is a massive Red Supergiant star
over 400 times the diameter of our Sun. It is
about 500 light years from Earth and is rapidly
and ominously burning itself up. Press [G] to
go there and zoom in with the [Home] key.
The view of the amazing star in front of you is
Figure 12 – the ominous surface of Betelgeuse
based upon what we can make out of its
surface from our best Earth telescopes. It has
a multicolored surface, with regions that are
hot and others that are cooler, making them look black in comparison. Don’t be fooled, however.
This star is a monster and someday, it is going to undergo a cataclysmic explosion known as a
Supernova (see later discussion) When it does, it will become the brightest object in the sky next to
the Sun for several weeks, possibly even outshining the moon. It may even shower Earth with
dangerous radiation that could endanger life on our planet. What is so strange is that it is so far away
(500 light years), that it takes light 500 years to get here from there. It may already have exploded
centuries ago, but the radiation and light is still in route; to arrive tomorrow … or in 300 years.
77. Next, press [Enter] and type the word, “Antares”. Press [Enter] again, then [G] to go there. Zoom
in close. Antares is also a Red Supergiant star. It is about 15 times the mass of our Sun, is 11,000
times brighter than our Sun now and over 400 times wider in diameter. Speed up time with the [L]
key to 100000x faster until Antares is turning slowly in space. Are you ready for this? Antares is so
large that 91 million (91,000,000) of our Suns could fit inside it. It also has a companion, another
large blue-white star that orbits it. Antares is not the biggest Red Supergiant we have ever found,
however. That distinction goes to Mu Cephei, a truly colossal star over 5,000 light years from Earth.
Fortunately, our Celestia computer database includes the star and our ship can take you to it.
78. Let’s visit it. Click here. Incredible, isn’t it? Its radius is unbelievably almost 1,100 times wider
than our Sun. To understand that size, if Mu Cephei was a sphere the diameter of a 20-story office
building, our Sun would be the size of a golf ball. Good Grief!!! We really do not want to be around
it when it finally ends its life in a colossal explosion. The explosion for a short time, will be one of
the brightest lights in the entire universe.
Celestia Educational Activity 6 – The Life and Death of Stars
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5. The Death of Earth (and the inner planets)
79. What of the planets that might be around a star that has swelled to a Red Giant or Supergiant? The
answer is not good. As the star swells, it will get big enough to actually swallow any planets that are
within 100 to 200 or so solar radii of it. The planet is consumed inside the fires of the star. Planets
that are further away may be spared, but they will get much hotter as the surface of the Red Giant
reaches toward them, sometimes hot enough for rocks on them to begin melting and gas atmospheres
to vaporize into space. The planets far from the star, however, can enjoy a time of mild warmth, as
the Red Giant finally warms their environment.
80. When the time comes, our Sun will get big enough to swallow and consume Mercury and Venus.
Astronomers are divided on whether its size will swell to engulf Earth. Some believe it will, others
are not sure. In either case, about 5 billion years from now, our beautiful planet will come to an end,
either swallowed and vaporized into atoms inside our Sun, or located so close to it that it melts and
becomes just a boiling blob of molten rocks. Mars will get very hot but will survive. Jupiter and
Saturn will get hot, and Uranus, Neptune and Pluto will be bathed in dangerous radiation. If humans
are still around when our Sun swells to a Red Giant billions of years from now, we will have to
abandon Earth and move beyond Neptune to our outermost planet, Pluto, if we ever hope to survive as
a species of life.
81. Through the magic of Celestia, we are going to take you to that time and place. You will get to
witness the death of our beautiful home as we know it. Are you ready?
82. Let’s travel far into the future aboard the Celestia 2, to a time billions of years from now. Our Sun
has run out of hydrogen fuel in its core. Gravity has caused it to shrink and heat up internally, as the
crushing pressures shoot up its core temperature to over 100 million degrees. Suddenly, Hydrogen
fusion begins again around a gas shell surrounding the core, and the internal core begins undergoing
Helium fusion also. Within days to weeks, our Sun explodes outward, rapidly swelling to a diameter
beyond the planets of Mercury and Venus.
These planets are swallowed and evaporate
inside the Red Giant. Still the surface of the
Sun swells and approaches … Earth. Gravity
grabs the exploding star and begins to slow its
swelling, but …
83. Return to Celestia and press the [V] key until
the information text disappears, then click
here.
84. The wounded dying planet in front of you is …
Earth, our home. Gone are its blue oceans and
Figure 13 –The Earth, melting as our Red giant Sun
pale blue atmosphere, its forests and animals,
approaches it
its birds and people. The planet is melting ... it
is already semi-molten. Surface temperatures
exceed 2000° F and rocks are melting back into the lava from which they originally formed. Watch
for a minute or two. If humans still exist as a species billions of years from now, we will have had to
abandon the Earth centuries earlier. … And the source of all that heat? It is just to the left of Earth.
To see what our Sun will become, tap your [4←] key on the numeric keyboard a few times.
85. Incredible, but true. Our Sun will someday swell to this size and look just like this. Earth will be
doomed. Left-click on the Sun to select it and press the [F] key to follow it. Zoom out with the
Celestia Educational Activity 6 – The Life and Death of Stars
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[End] key if you wish. Then, Right-click-drag around it. Unfortunately, the Sun has not yet reached
its final equilibrium size. As each day passes, it continues to swell, getting closer and closer to Earth.
86. If the Sun does reach the orbit of Earth our planet will melt, then turn to gases and vaporize within the
fiery sphere of our Red Giant Sun.
87. To visit that time and place, click here. You are actually now inside the Red Giant’s fiery atmosphere.
The Earth has melted and vaporized. This is its final resting place. Its atoms and molecules,
including those of all the plants, animals and people who ever lived on Earth, will become part of our
Sun again. Perhaps it is somehow fitting that Earth formed from the gases and dust of that original
nebula gathered by our Sun when it first developed, and it will die by having those same atoms merge
again with the Sun. Since your atoms are a part of Earth, your atoms also will someday merge with
those of your Sun.
88. What of the other planets? Once our Sun reaches it final Red Giant equilibrium size, it will stay that
size for millions of years. Could humanity move to Mars and set up a new home there … or perhaps
to a moon of Jupiter?
89. To find out, click here. You will be taken to a position in space locked onto … Mars. It is that tiny
red dot to the left of the swollen and bloated Red Giant Sun. Do you see it? Press the “[G] key and
your ship will take you there. As you can see, Mars is not a home for humanity. It is so close to the
Red Giant that it too is melting. Its surface temperature is very hot. Its atmosphere has also blown
away and its ice caps have long ago melted and vaporized into space.
90. Press and hold down the [Shift + left ← ] keys together and see what the doomed and cooked Mars of
our future will look like.
91. Jupiter also and all of its moons will be too close to our Red Giant star to live comfortably. Jupiter of
course, is a gas giant planet and has no solid surface. However, it has over 60 moons and all of them
are rocky, with large pockets of ice. Ganymede and Europa for example, are large moons that have
extensive water. They are large enough to hold onto a thin atmosphere that could support life.
Unfortunately, our Red Giant star is expected to make even the Jovian (Jupiter) system too hot. To
see why, click here. The Red Giant on the right will far overshadow tiny Jupiter, just visible near the
left side of your view window. Press the [G] key to go to Jupiter. When you get there, press and hold
down the [Shift + left ← ] keys together. Your ship will rotate around Jupiter and you will see it as it
might look billions of years from now. Its clouds will be different and it will have a distinct reddish
glow from the light of the star. Its atmosphere will be puffed out from the heat of the Red Giant.
92. To sense what Jupiter is like, position yourself
behind the planet with the Red Giant in front of
you (see figure 14). Press the [\] key to resume
Real time, and the [V] key to restore your HUD
text. Now, press the [A] key and accelerate
toward the planet at 4000 – 5000 km/s. If you go
too fast, slow down with the [Z] key. Steer your
ship and fly above Jupiter (don’t crash). When
you pass the planet and it is behind you, press the
[Shift and *] keys together to turn on your rear
viewscreen. You can watch Jupiter recede from
you. When done, press the [Shift+*] keys again
to restore forward view.
93. Press the [S] key to stop your ship.
Figure 14 –
our Sun
from Jupiter
Celestia Educational Activity 6 – The Life and Death of Stars
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94. Jupiter and all of its moons will be bathed in heat and electromagnetic radiation too severe and harsh
for any life to survive. Even the rocky, ice covered moons of Saturn and Uranus will receive too
much radiation to support life safely over the long term. Based on our latest estimates, humanity will
have to travel to the farthest moons of Neptune or to our outermost planet, Pluto, to survive the fierce
energy pouring out of this Red Giant.
95. Far in the future, if humans are still around, we will have prepared for the end of Earth, and may have
moved our civilizations to Pluto and its moon, Charon. Let’s go there now, and see what awaits us.
6. A new Beginning on Pluto?
96. To go to Pluto, click here. Your ship will fly you at hyperspeed to New Pluto space. This tiny world
has become the new home of humanity. Zoom in. To see all of the cities, speed up time with the [L]
key to view the planet rotating before you, its cities turning on their lights as Pluto turns into the dark
side. To see its new and advanced civilization, right-click-drag around the planet. In the distance,
the Red Giant glows with heat, fainter and cooler way out here, but still warm enough to keep this
world alive and give us a home.
97. Swing the planet around and look for Pluto’s brown moon Charon in the distance. It too has extensive
cities and colonies, visible as it too rotates beyond your ship.
98. When done, resume Real time with the [\] key.
99. Answer all questions about the Red giant stage of a star life cycle. Go to Worksheet.
7. The Death of a Red Giant Star – the Planetary Nebula stage
100. Billions of years from now, our Red Giant Sun will burn helium in its core and fuse it into Carbon,
Oxygen, Neon and a few other elements. Eventually, however, it will run out of helium fuel in the
central core. When that happens, fusion will again stop and again, gravity will grab the star’s internal
mass and compress it, crushing it toward the center of the star. The Red Giant’s core will shrink in
size. It will happen fast, in a matter of weeks to months. Again, temperatures will skyrocket in the
core, this time to impossible temperatures approaching hundreds of millions of degrees.
101. Once again, as temperatures get to such a fierce level, the remaining helium surrounding the now
stupendously hot core will be compressed by gravity and again begin fusing in a shell of helium
fusion. Beyond that, the remaining hydrogen in the star will begin fusing in a much larger, outer shell
of fusion. This will swell the star outward again. It will happen quickly. The star will explode again
from the truly enormous energies released by such fusion. This time, however, gravity will not be
able to hold the star in one piece. Entire layers of the Red Giant sun will be blown away and be
thrown into space, expanding as a ring of debris called a Planetary Nebula (the name has nothing to
do with planets). The remains of the star will temporarily stop fusing, gravity will grab what’s left of
it and compress it and again, intense fusion will occur in shells around the core, causing another giant
Celestia Educational Activity 6 – The Life and Death of Stars
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explosion and another layer of the Sun will be thrown off. Piece by piece, layer by layer, our Sun will
puff up and blow itself to bits, coughing out parts of itself like smoke rings.
102.
The layers flying off the Sun form a glowing cloud of debris in space called a Planetary Nebula.
103. When our Red Giant Sun does finally explode layer by layer, it will signal the end for most of the
remaining planets in our Solar System. The shock waves and heat from the explosions will incinerate
Mars, Jupiter and Saturn, and all of their moons. The shock waves from the expanding debris will
deform and possibly blow apart the atmospheres of Uranus and Neptune, an enormous “solar wind”
that knocks the gases of the outer giant planets into space. Although Pluto may survive the initial
blasts, no human colonies living on it will be able to do so and will be destroyed. In the end, the Sun
will lose so much mass that what is left of our solar system including Pluto will either be blown out of
orbit and become adrift in space, or be forced to orbit what is left of our Sun at vast distances far
beyond their current positions, alone in the frigid cold and darkness of space.
104. Such explosions signal the beginning-of-the-end of the life cycle of a main sequence star similar to
our Sun in size, and its Solar System. Over 99% of the stars you see in the night sky will have such a
fate. The universe is obviously full of the recent remains of such explosions. Lets’ visit four of them
now in the Celestia 2.
105.
Press the [Enter] key and type “Eight Burst Nebula”. Note: Your ship’s computer will try to
guess where you want to go and display a list below your typing. If you see the name, press the [Tab]
key to cycle through the choices. When you stop on the one you want, just press the [Enter] key
again and [G] to go there. You will be whisked to a place where a Red Giant star exploded thousands
of years ago. Its remains are present now only as an expanding “shell” of gas and atomic debris that
is spreading into surrounding space at a speed of
Figure 15 –
thousands of miles/km every hour. It is made of many
the Helix
of the lighter elements in the periodic table, from
Nebula
hydrogen to iron. Year by year, this Planetary
Nebula gets wider and dimmer. Zoom in with the
[Home] key if you wish and just enjoy its tragic
beauty for a moment.
106. Stop two is to the Helix Nebula. Press the [Enter]
key and type “Helix Nebula”. Press [Enter] again
and [G] to go there. What a dramatic series of
explosions, tossing off several layers that are still
glowing with energy as they spread out.
107. Our third stop will take you to an older Planetary nebula. This one has been expanding a long
time in a nice round spherical shape. You can see through it, in fact. It is called the Abell 39 nebula.
To go there, click here. Wild, isn’t it. Right-click-drag around it. It really is here in space and looks
just like this.
108. Lastly, click here to go to the famous Ring Nebula. Notice the extent of explosive layers in this
nebula. Imagine the fate of any planets near the central Red Giant when it finally ran out of fuel and
blew up in a final set of explosions.
109. Where will all of those newly created atoms go as they spread into space? The answer is … quite
amazing. They will merge into space, mixing with other thin nebula gases that are already there.
Sometime far in the future, they may in fact, become part of a new nebula cloud that is pulled by
gravity into a new protostar. In short, the atoms that these exploded stars forge in the furnace of its
exploding core may one day recycle and become a new star … or a new planet.
Celestia Educational Activity 6 – The Life and Death of Stars
pg 22 of 29
110. In fact, you live on such a planet. We are made of such atoms. You have large amounts of carbon
and oxygen, nitrogen and calcium in your bodies. The atoms that make you up came from the Earth
and the Earth in turn is made of atoms that were created in the heart of an exploding planetary nebula
and supernova (more about that shortly) long ago … a star that threw its debris far into space, to
become incorporated into the nebula that our Sun and solar system eventually formed from. In a way,
we and all life on Earth are related. We are all “children” of the universe.
111.
Complete the questions on the Planetary Nebula stage in the worksheet. Go to Worksheet.
8. The White Dwarf and Black Dwarf Stages
112. Look in the center of the ring nebula and you will see a small white star. In fact, this is all that
remains of the central core of the massive Red Giant star that blew up here. As it blew up, pieces of
its mass were thrown into space to form that nebula, but some of its densest core remained, held
closely together by gravity. Over time, gravity compressed that dense material into a super-hot ball of
elements called a “White Dwarf”. A white dwarf could still be considered a “star” because it glows
very bright for its tiny size, and is ferociously hot (hundreds of millions of degrees) from the heat of
that fiery explosion. However, it is actually better considered a huge hot ball of debris. It is no longer
fusing elements; it is not burning anything anymore. It is just a super-dense pile of rubble, tightly
packed into a glowing hot ball perhaps the size of the Earth (only 1/10,000th the size of the Red Giant
from which it remains).
113. All stars that explode into planetary nebula will leave a white-hot dwarf remnant, a core of debris.
When our Sun explodes in the future, it too will leave a white dwarf.
114. Let’s visit two white dwarf stars. You’ll discover something very unusual about them. To go to
the first, click here. It is the White Dwarf imbedded in the Abell 39 nebula that you visited a bit ago.
Time has not been speed up but is passing as Real time. What do you notice about a White Dwarf’s
rotation rate? Go to Worksheet.
115. White Dwarfs are also very very hot! White Dwarfs may not be fusing elements, but they are the
very dense remains of an explosion that reached a temperature of 200 – 400 million° F. Even in the
cold of space, their dense mass takes billions of years to cool off. They also spin … fast. Gravity
forces them to rotate rapidly on their axis,
due to a law of Physics known as the Law
of Conservation of Angular Momentum.
As they spin and cool slowly, their
brightness and color will begin to fade.
Over billions of years, they will change
from bright white to yellow, to orange,
then to a Red Dwarf. Eventually, they will
fade to brown in color and finally … to
black. They will cool down to a frozen
Figure 16 – a
temperature exceeding -400° F below zero
White Dwarf star
and become just a cold, dense black
“lump” of stellar debris in space. It is not
Celestia Educational Activity 6 – The Life and Death of Stars
pg 23 of 29
clear how many Black Dwarfs actually populate the universe yet. The time for a White Dwarf to cool
to black is estimated in 10’s to 100’s of billions of years, and the universe may not yet be old enough
for many White Dwarfs to have cooled down to black.
116. The Celestia 2 is programmed to take you to an older White Dwarf, adrift in the Milky Way just
15 light years from Earth. To do so, click here. The white dwarf in front of you is named Van
Maanen’s star or Wolf 28 (named after the men who found it independently). It has slowed down a
bit from TYC-2-900-0 due to its age and has cooled off somewhat. What is amazing, however, is the
fact that it will still spin like this silently in space here for billions of years more (it makes no noise),
slowly fading in color and temperature … slowly cooling off.
117. What will the end of our Sun’s life cycle look like? Let’s visit a theoretical “Black Dwarf”. Click
here. In the distance, almost invisible, is a model of a fading black dwarf. It is centered in your
screen. Can you see it? If not, right-click-drag and see if you can find it. Press the [G] key once
to go to it and tap the [L] key once. If we could visit a Black Dwarf, this is all that would remain
of a once mighty star. It is fading now. Its spin has slowed to a crawl. Just a dim glow remains of
the fires that once powered this star. The nebula that it threw off is long ago gone, spread out into
wisps of gas and dust in space. In a few billion more years, this dim glowing blob of matter will be
as black as the blackness of space. Here, it will drift throughout the Milky Way, possibly for as
long as our galaxy lasts. If it once had planets, most would be long destroyed or lost to space. It is
possible, however, that far from this dwarf, there may still be a few lone asteroids or frozen comets
or even a small planet remnant circling it, orbiting it in a cold lonely dance that will continue
forever. This is the end of a star the size of our Sun. This will be the end of our Sun also. Return
to Celestia and contemplate it for a few moments.
118. Go to the worksheet and complete all questions on White and Black Dwarfs. Go to Worksheet.
9. The Death of Large Stars – Supernova Stage
119. What of the giant stars, the massive Red Supergiants like Betelgeuse or Mu Cep? Will they also
end their lives in a series of explosions, producing a series of expanding shells of gas (planetary
nebula)? The answer is no! Their fate is much more violent … and unbelievable!
120. When a Red Supergiant runs out of helium fuel, its
nuclear fires in its core calm down and like its smaller
cousins the Red Giants, gravity pulls it inward and it
collapses. Again, its core, which is now primarily
carbon and oxygen, heats up as gravity collapses the
star, shrinking it in size to a diameter not much larger
than Earth. The core’s temperature and pressures now
skyrocket to levels almost impossible to conceive …
temperatures far above a billion degrees. There, an
enormous amount of atomic mass, far more than a
normal Red Giant, is ready to blow. At that point ...
Figure 17 – a Red Supergiant goes
Supernova
Celestia Educational Activity 6 – The Life and Death of Stars
pg 24 of 29
121. The entire Red Supergiant’s core begins fusing into heavier and heavier elements, virtually all at
the same time. In a few seconds, nuclei are crushed into each other with such force that ALL of
the 90 elements in the Periodic Table are created. This furious fusion inside a celestial body
millions of millions in diameter causes the star to explode with a force that staggers the
imagination. The explosion is called a Supernova!
122. Gravity has no chance of containing such an explosion. The star is literally blown to bits in a
cataclysmic explosion of epic proportions. It disintegrates and rushes outward at enormous speed
of several million miles/km per hour.
123. A major part of the star’s mass is thrown into space. All of the newly formed atoms and nuclei that
were created by fusion near the core in a few moments, become debris shot at high speed into
space. Over time, that debris will mix with hydrogen, helium and other atoms from other star
explosions in space and become part of a new nebula. Millions, perhaps billions of years later, a
new star may form from that nebula material … a star with planets and a solar system.
124. As you read this, realize this! The hydrogen in your body dates back to the beginning of the
universe over 13.7 billion years ago. The carbon that makes up your muscles, skin and bones came
from an exploded planetary nebula some time billions of years ago. The heavier elements in your
body, such as magnesium, potassium, iron, silicon, etc. were formed inside the core of a massive
Red Supergiant star that exploded in a Supernova explosion over 6 billion years ago, somewhere in
our area of space. Our Sun and all of its planets and moons (including Earth), formed from part of
that nebula. You are literally made of the stuff of a violent universe.
125. To see an animation of what a Supernova might look like, click here and wait for the movie to
open. Press [Alt + Enter] to go to full screen. Press again and close the movie screen when done.
126. The Celestia 2 is ready to take you to a Supernova explosion in space. Press the [Enter] key, type
“M1”, press [Enter] again and [G] to go there. You will be flown at hyperspeed to the location of
one of the largest explosions ever to occur in the neighborhood of our part of the Milky Way. You
are looking at the Crab Nebula. Zoom in to a distance of about 10 ly.
127. In the year 1054 CE, some folks in China noticed a bright star in the sky that suddenly appeared. It
was visible even in the daytime for several weeks. Within a few months, its brightness had faded
to a dim glow, visible only at night. They recorded the sighting and position in some ancient
writings dating from that time.
128. Today, modern telescopes have found that location and have discovered ... the Crab Nebula. It is
the site of a Supernova explosion less than 1000 years ago. It is a long way from our Sun (over
6,000 light years), but that is good. Had it been much closer, the Earth would have received not
only visible light from the explosion, but some of the deadly radiation that poured out of the Red
Supergiant that blew up here. Had it been 100 times closer to Earth when it blew, it could have
caused a mass extinction of much of life on Earth, and none of us would be here today.
129. The Crab Nebula is one of hundreds of such locations that have been chronicled in our night sky.
The stellar debris you see as colored nebula represents all 90 elements (they glow different colors).
It is still expanding, spreading into space at high speed. It will continue to do so for thousands of
years. Slowly, that debris will mix with the gases of deep space and will stop glowing. Hundreds
of thousands of years from now, the Crab will fade from view. Those atoms, however, will remain
in space, available to form new stars someday, should gravity re-organize this region of space into
a new stellar nursery.
130. Answer the questions on supernova. Go to Worksheet.
Celestia Educational Activity 6 – The Life and Death of Stars
pg 25 of 29
10. The Death of Large Stars Neutron Star and Pulsar Stage
131. From our earlier discussion, please recall that when a Red Giant blows up, some remnant of the
core remains as a super-hot, dense White Dwarf. Well, something similar occurs when a larger
Red Supergiant star blows up in a Supernova explosion. This time, however, things get really
strange.
132. A supernova explosion is so enormous that when it blows, the energy is sent in all directions at
once. Not only does the explosion expand outward, but it also squashes inward. The central core
of the massive Red Supergiant is compressed by such titanic forces so hard, that the matter trapped
there is squashed into a sphere no bigger than about 10 miles across.
133. That sphere is called a Neutron Star. It has that name because the compression and enormous
forces change the nuclear structure. The electrons and protons that make up a large part of the
mass of all stars are crushed together so severely that they merge and become neutrons. The entire
central core of the exploding Supernova becomes one, incredibly dense, squashed, super-hot mass
of neutrons.
134. The properties of a Neutron Star are so strange that they are hard to believe. First, they are the
most dense objects in the visible universe. The neutrons are packed so tightly together that there is
simply no empty space ... neutrons are practically touching each other. There are so many of them
that the mass of an entire star is packed into a volume only a few miles across. This results in
gravitational forces being emitted so powerful that if you could somehow collect 1 teaspoon of a
neutron star, it would weigh close to 100 million tons. Imagine it … a teaspoon weighing 100
million TONS. If you put such a weight on the ground of Earth, it would instantly disappear into
the ground, boring its own hole all the way to the center of the Earth. Were you to get too close to
a neutron star, its gravity would pull you and your ship down to it to splat onto its glowing solid
surface like a drop of hot oil on a hot skillet. Every atom of your body and ship would be plastered
against the surface of the star and ripped apart to be converted to neutrons. In short, you would
become a very thin, super-hot, neutron film smeared onto the star (Ugh!).
135. A second amazing fact is a neutron star’s spin. As it is crushed into a tiny ball during the
supernova explosion, the mass of a neutron star begins to spin as it shrinks and packs more tightly
together. It is the same principle that causes white dwarfs and nebula and stars to spin … the
principle of Conservation of Angular Momentum. In this case, a neutron star’s spin becomes
incredibly fast. A newly formed neutron star will spin on its axis faster than an ice skater spinning
in her best pirouette. The spin can exceed a whopping 50 times a second. As it spins, a neutron
star is also hot … incredibly hot. It is truly a hot, blue-white whirling demon!
136. To witness a neutron star up close and personal, click here. The Celestia 2 will take you safely to
the outskirts of one. Press the [A] key and accelerate to between 5 – 6 km/s. As the star
approaches, tap the steering keys and fly closely by it on the left or right. After you pass it, press
the [S] key to stop your ship.
137. Although no nuclear fusion is occurring, energy and heat are pouring off the star. As such, Neutron
stars are just like White Dwarfs. They are super hot, they spin, and they take billions of years to
cool off. Eventually, they too will end their existence as a Black Dwarf.
Celestia Educational Activity 6 – The Life and Death of Stars
pg 26 of 29
138. Sometimes, however, nature has an even
weirder surprise. Whenever a Supernova
explodes, titanic magnetic forces are also being
generated around the star. In some newly
formed neutron stars that are still surrounded
by the debris from a recent supernova
explosion, gravity will pull that supernova
debris down toward the neutron star,
accelerating it to enormous speeds. It will then
impact onto the surface of the neutron star.
The result is what can best be described as a
“squirt”. Matter circles the neutron star as it
Figure 18 – the Pulsar
falls in and some of it is squirted back away
from the star at high speed, channeled into two
narrow beams of matter called “jets” by the steering effects of the magnetic fields. Sometimes the
jets point away from the Earth and we don’t see them. Sometimes, however, they point directly at
Earth. As the star spins, what we will see is twin concentrated jets of matter going by rapidly. The
star will appear to pulse or blink. If it does, the neutron star is called a Pulsing Neutron Star, or
Pulsar for short.
139. The Celestia 2 contains a pulsing neutron star in its database. In fact, it is inside the Crab Nebula.
The neutron star that formed inside the Crab is in fact, a Pulsar. Its jets happen to be pointing
toward Earth. Let’s go there again. To do so, click here. Then press the [G] key. When you get
closer, zoom in with the [Home] key.
140. The Crab Pulsar is spinning 32 times per second. To stop its spin a moment, press the [Spacebar]
at the bottom of the keyboard. This pauses time. Press it again to resume Real time. The jets of
beamed energy sweeping across your ship are in fact, horrendously deadly. They are concentrated
beams of high-energy photons that would kill you instantly if your ship did not have good
protection. The gravity from the neutron star is also pulling you toward it. Only your ship’s
automatic controls are keeping you from splatting onto the surface.
141. This pulsar is really there in space at this spot and will spin like this for millions of years. Slowly,
over time, the spin will slow down. The rest of the supernova gases that are feeding this hot core
will slowly spread out across space and the neutron star will run out of material to fall onto it. The
jets will die away. Its color will fade from white hot, to red, then to maroon, then eventually to
black. Billions of years from now, this neutron star will become a super-dense cold and dead
Black Dwarf, drifting through the galaxy like all of its brethren.
142. Complete the questions on Pulsars. Go to Worksheet.
Celestia Educational Activity 6 – The Life and Death of Stars
pg 27 of 29
11. The Death of Large Stars The Black Hole
143. The universe is surely strange, but it has left its strangest thing for last.
144. On a rare occasion, a REALLY BIG Red Supergiant blows up in a supernova explosion (a star like
Mu Cep or Antares). When that happens, the core of the star will be crushed inward and a neutron
star will form. However, … gasp! … scientists have discovered that if there is enough material
available to be crushed, the diameter of the neutron star will not stop at 10 miles or so. It will be
crushed to a size so small that the object becomes “impossibly” dense. It is crushed far beyond the
neutron star stage. All of its neutrons in fact, become crushed by the explosion so much that they
literally squash “out of existence”. They stop being made of matter. They become … well ….
nothing! They actually disappear from the universe. They create a “hole” in space itself. The hole
is very tiny. In some cases, it can be smaller than the nucleus of an atom. It is called a singularity.
This place … this hole in space … is called a “Black Hole”. It really is black. Gravity is so strong
here that nothing, not even a beam of light, can escape. Nothing that falls into or is sucked into a
Black Hole is ever heard from again. Even light falling into the hole disappears.
145. The gravity of a Black Hole is so strong that even space itself is sucked into it for some distance
around it (Huh????). The tiny singularity in the center creates a bigger zone of complete blackness
around it that may be 10 miles or more in diameter. The edges of that zone are called the “event
horizon”. Anything … matter, light and space itself … within the event horizon is sucked out of
existence. Nothing can be seen coming from it.
146. What would a Black Hole look like? Let’s go find out. Click here. You will be taken far from our
solar system to a place where very long ago, a massive supernova explosion occurred. The nebula
cloud of debris has long ago spread out into space or been sucked into ? Nothing is visible except
stars, the Milky Way galaxy and … a Black Hole. Can you find it? It is small and silhouetted
against the haze of the Milky Way. Search carefully. To go to it, press the [G] key.
147. The Black Hole in front of you is spinning at close to 100 times per second. Although it is a “hole”
in space, it is a spinning hole. It is the weirdest thing to try to imagine. Its gravity is so powerful
that if you were in front of it in real space-time, your ship, your body and every atom in you would
be instantly ripped apart and be sucked down into that black tear in space. The eerie glow around it
is actually wisps of stray interstellar gas being sucked into the hole and falling inward, glowing as
it accelerates and disappears from the universe forever, almost as if the gas was “screaming” as it
fell in.
148. Because the star it formed from once orbited the Milky Way as one of billions of such stars, so
does the Black Hole. It moves silently and eerily through space, orbiting the Milky Way at a
similar rate as its now destroyed parent star, silent and deadly, a one-way trap to oblivion.
149. As it moves, Black Holes can encounter other objects. On occasion, things do get too close to a
Black Hole. Entire stars, dense nebula gases, planets … anything that strays too close will be
ripped apart by the gravity and sucked into the hole, disappearing forever. When that happens, the
gases and atoms falling into the hole accelerate to very high speeds as they are sucked in. The
atoms collide with each other on the way in and frequently will glow with energy as they are ripped
apart. That glow is visible to us folks on Earth as a glowing “disk”, spiraling around the jet-black
event horizon of the hole in the center. It is called an “Accretion Disk”.
150. The Celestia 2 is programmed to take you to a rotating Black Hole with an accretion disk of matter
falling into it. To go there, click here.
Celestia Educational Activity 6 – The Life and Death of Stars
151. That colored disk is nebula and star
material being sucked into the black hole.
As it does so, it is rotating around the hole.
Let’s challenge your ship and you in
piloting skills. Aim for the rim of the
accretion disk and press the [A] key to start
your engines. Accelerate to about 2.5 km/s
and fly toward the black hole, skimming
just along the top of the accretion disk (see
figure 19). At the last minute, pull up, or
even the Celestia 2 will not be able to save
you from instant destruction.
pg 28 of 29
Figure 19 – being sucked down
a Black Hole
152. Black Holes appear to exist forever. Once
“space” itself is punctured with this incredible object’s presence, we do not believe a repair occurs.
The “hole” stays there, drifting through space. Right now, a Black Hole could be drifting through
our part of the Milky Way galaxy. Someday, one could even drift into the neighborhood of our
Sun. If that occurred, it might be possible that our solar system (and us along with it), could be
sucked into the passing hole. That would be the end … of us.
153.
In summary, the life of a massive star ends when it blows up in a supernova explosion and its
remaining core forms a Neutron Star, which may or may not become a Pulsar. In either case, the
neutron star or pulsar will eventually become a cold Black dwarf. A supernova core, however, can
instead quickly compress past the neutron star stage directly into a rotating Black Hole.
12. Conclusion
154. We hope you have enjoyed this celestial journey into the life cycle of stars aboard the Celestia 2. If
you have not done so, we urge you to explore our other Celestia activities and enjoy the program
on your own. Our new educational website has great facts and pictures about this amazing universe
we call home.
155. If you have been taking this voyage of discovery as part of a school lesson, and have been writing
your answers on a printed worksheet, it is time to turn your work into your teacher. Make sure
your name is on the top of the worksheet. To close this document, simply click the small “X” in
the top right corner, or follow your normal procedures for closing documents, if you are running
another operating system. You may close Celestia or continue exploring the universe on your own.
We urge you to journey through other Celestia Educational Activities at http://www.fsgregs.org/celestia
or at the Celestia add-on repository at http://www.celestiamotherlode.net
Celestia Educational Activity 6 – The Life and Death of Stars
pg 29 of 29
13. Credits:
This document was written by Frank M. Gregorio, Manassas, VA
Version 6, rev 4. revised September, 2004
Copyright © 2003, 2004 - Frank M. Gregorio
Celestia – courtesy of :
Chris Laurel
Clint Weisbrod
Fridger Schrempp
Bob Ippolito
Christophe Teyssier
Copyright © 2000, 2004 - Chris Laurel
Many thanks to the gifted artists and graphics designers who contributed add-on textures to this Activity.
Star Textures - Copyright © and courtesy – Kris Rassilon
Red Giant texture - Copyright © and courtesy – Kris Rassilon
Dying Earth Textures - Copyright © and courtesy – Don Edwards
Dying Mars Textures - Copyright © and courtesy – Kris Rassilon
Dying Jupiter Textures - Copyright © and courtesy – Kris Rassilon
New Pluto and Charon textures - Copyright © and courtesy – Don Edwards
Protostar textures - Copyright © and courtesy – David Nessler
Protostar with jet textures - Copyright © and courtesy – Kris Rassilon
Brown Dwarf - Copyright © and courtesy – Frank Gregorio
Betelgeuse Surface texture - Copyright © and courtesy – S. Bowers
Neutron star - Copyright © and courtesy – Frank Gregorio
White Dwarf - Copyright © and courtesy –
Black Hole Accretion Disk- Copyright © and courtesy - Jorge Omar Leyra
Black Hole 2 texture - Copyright © and courtesy – Frank Gregorio
Black Dwarf - Copyright © and courtesy – Frank Gregorio
Orion Nebula - Copyright © and courtesy – Mind-toAsk
Eagle nebula - Copyright © and courtesy – Mind-to-Ask
Crab Nebula - Copyright © and courtesy – Killeen
Rosette Nebula and planets - Copyright © and courtesy – Kris Rassilon
Pulsar Model - Copyright © and courtesy – Kris Rassilon
Ring Nebula - Copyright © and courtesy - Vandenrijt Jean-François
Eight Burst nebula - Copyright © and courtesy – Killeen
Abell 39 nebula - Copyright © and courtesy – Astroboy
Helix Nebula - Copyright © and courtesy – Astroboy
Supernova animation - Copyright © and courtesy – NASA Hubble Space Telescope Institute
Supernova drawing © 2003, Patrick Towen
Pulsar Drawing © 2002, David King
Nebula Solar Wind drawing - © 2002, David Hardy
Permission is granted to copy and distribute this document under the terms of the GNU Free Documentation License, Version 1.1 or any later
version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
A copy of the license is included in "GNU Free Documentation License".