Download In Pictures: Journey to the Stars

In Pictures: Journey to the Stars
This text is provided courtesy of OLogy, the American Museum of Natural History’s
website for kids.
Hi, we're Mordecai-Mark Mac Low and Rebecca Oppenheimer. We are astrophysicists at the
American Museum of Natural History. Did you know that stars are really important to us? In fact,
they make all life possible. Let's find out why!
In college, Mordecai-Mark Mac Low decided to take
science classes that looked like fun. So he chose
astrophysics, which uses physics to under- stand
how the universe works. Today, he's an
astrophysicist, studying how stars, planets, and
galaxies form. Since these process take millions of
years, he models them using computer simulations.
Then he compares the models
Image credits:© AMNH/D.Finnin; Mordecai-Mark
Mac Low: courtesy of AMNH /D. Finnin.
As a kid growing up in New York City, Rebecca
Oppenheimer always wanted to study stars and planets.
She never dreamed she would someday discover an
entirely new kind of object. In 1995, she observed a small,
dim object that was neither a planet nor a star. It is called a
brown dwarf. This observation shows us that there are still
things left to be discovered in the universe. Rebecca also
studies faraway planets, and dying stars called white
dwarfs.
Image credits: courtesy of AMNH / D. Finnin.
Twinkle, twinkle, little star... On a clear night, we can see thousands of stars with our naked
eye.
© AMNH
A star is a huge glowing ball of hot gas. Deep inside its core,
hydrogen atoms smash together, forming helium and
releasing huge amounts of energy that heats the gas. This is
called nuclear fusion, and it’s why a star shines. As the hot
gas pushed outward, it opposes the inward pull of gravity.
This balance of forces is what makes a star, a star. It holds
the star together and keeps it at a steady temperature for
most of its life.
Image credits: © AMNH; Mordecai-Mark Mac Low: courtesy
of AMNH / D. Finnin.
In the Milky Way Galaxy alone, there are hundreds of billions of stars. And
there are many more in the universe. But did you know that a long, long time
ago, there were no stars at all?
© AMNH
In the Milky Way Galaxy alone, there are hundreds of billions of stars. And there
are many more in the universe. But did you know that a long, long time ago, there
You have to be a really big thinker to imagine
Theno
Milky
Way is
galaxy in which our Solar
were
stars
attheall?
System lives. There are more than 200 billion
stars in our spiral galaxy, and our Sun is just
one of them. Even if you traveled at the speed
of light, it would take you about 1000,000
years to get across the Milky Way.
Image credits: The Milky Way in Infrared,
courtesy of The COBE Project, DIRBE, and
NASA; Mike Shara: courtesy of AMNH.
the size of the Universe. It’s so big that light
from the most distant galaxies takes over 10
billion years just to reach us on Earth! That’s
twice as long as Earth’s been around. Everything
we’ve ever observed in space is part of our
Universe. We don’t know what’s beyond it or if
there are other Universes out there.
Image credits: The image of the universe ©
American Museum of Natural History and the
National Center for Supercomputing
In the Milky Way Galaxy alone, there are hundreds
of 1999;
billions
ofLiu:stars.
And
Applications,
Charles
courtesy
of there
AMNH.
are many more in the universe. But did you know that a long, long time ago, there
© AMNH
were no stars at all?
Over 13 billion years ago, there was only an invisible substance called dark matter, along with
hydrogen and helium gas. Dark matter's gravity gathered this gas to form the first stars.
In the Milky Way Galaxy alone, there are hundreds of billions of stars. And there
are many more in the universe. But did you know that a long, long time ago, there
were no stars at all?
Gravity is the force of attraction between all objects in the
© AMNH
Universe. Objects with more mass have greater
gravitational
pull
than
objects
with
less
mass.
Gravity
keeps
Over 13 billion years ago, there was only an invisible substance called dark matter,
Earth and the planets orbiting around the Sun instead of
and heliumfloating
gas.offDark
matter's
gravity
gathered
into space.
What would
the Universe
be like this gas to form the first stars.
without gravity?
along with hydrogen
Over 13 billion years ago, there was only an invisible substance called dark matter, along with hydrogen
But the first stars didn't last long. They were massive. They burned hot, lived fast, and died
young. They blew up in gigantic explosions called supernovas.
Ninety-three million miles from Earth, a giant ball of hot
gas brightens the sky. Nuclear reactions in the Sun’s core
create energy, which gradually flows to the Sun’s
surface. This energy reaches Earth in the form of
sunlight. The Sun’s heat and light warm Earth’s surface,
drive weather and currents, and make life possible on
our planet. We experience the Sun’s energy every time
we feel its warmth on our skin or see with the aid of
sunlight.
The Earth is our home. So far, it’s the only place that we know of
that has life. Everywhere you look on Earth there is life. This is
possible because Earth has lots of water. It’s also just the right
distance from the Sun. Some people call Earth the “Goldilocks
planet.” It’s not too hot (like Venus), and not too cold (like Mars),
it’s just right!
Image credits: courtesy of NASA; Rosamond Kinzler: AMNH.
Image credits: courtesy of NASA; Neil Tyson: AMNH.
© AMNH
Stars are factories for new elements. As stars live and die, they form almost all of the elements
that we know of, like oxygen and carbon.
We see light every day -- whether from light bulbs, flames,
flashlights, or the Sun (our most important source of light). We
see objects because they reflect, or bounce, light into our eyes.
Light is a form of energy called electromagnetic radiation. It's
made of tiny particles called photons that travel in straight lines.
In a vacuum, nothing can travel faster.
Image credits: Eric Hamilton.
Earth orbits a star we call the Sun. It is a middle-aged yellow star that is more massive than the
average star.
© AMNH
© AMNH
The Sun is a star that powers our planet. It brightens our days and provides us with heat and
other forms of energy.
© AMNH
The Sun is a star that powers our planet. It brightens our days and provides us with heat and
other forms of energy. The Sun, like all the stars, is a huge glowing ball of hot gas. It gives off
energy as light that we can see-sunshine. It also gives off invisible light, such as ultraviolet and
radio.
Energy is the ability to do work. Scientists define "work" as when a
force moves something. When you lift a brick, you are doing work
because you are exerting a force to lift the heavy object.Energy comes
in many forms, such as heat, sound, light, electric, and chemical.
Energy easily changes from one form to another.
Image credits: Eric Hamilton.
© AMNH
At the end of its life, the Sun will become a red giant. It will blow its outer layers out into the
universe, seeding new stars and planets. But don’t worry. This won’t happen for 5 billion years.
© AMNH
Scientists observe stars using telescopes on Earth and in space. They see stars being born, maturing,
and at the end of their lives.
© AMNH
This is the Orion Nebula. Huge stellar nurseries like this are found all over the Milky Way and
other spiral galaxies.
Before telescopes were invented, people gazed at the night sky
with amazement and dreamed of a closer look. The invention of the
telescope in 1608 gave humans their chance to explore the vastness
of the Universe. In fact, most of what we know about the Universe
comes from studying the sky with telescopes. Telescopes use lenses
and mirrors to gather light and produce images. Galileo was the
first to use telescopes for astronomy.
Image credits: courtesy of AMNH.
The Orion constellation is known for having some of the brightest
stars in the night sky. On a clear night, try to find the three stars that
form the “belt” of the hunter. Above and below the belt you’ll see
Betelgeuse and Rigel. Betelgeuse looks reddish and Rigel is blue. The
cloudy area just below the belt is the Orion Nebula – the closest
major star-forming region to Earth.
Image credits: "Observers", "Institute", Sven Kohle and Till Credner.
A galaxy is a giant, spinning object made of gas, dust, and stars
held together by gravity. Galaxies come in different shapes and
sizes and can contain billions of stars. Most occur in groups that
are also held together by gravity. We now know that the
Universe has billions of galaxies, and the Milky Way is only one
of them.
© AMNH
Image credits: The Southern Pinwheel Galaxy from VLT, FORS
Team 8.2-meter VLT ESO Hubble Deep Field ,R. Williams and
the HDF Team (STScI) and NASA M31: The Andromeda Galaxy,
© and Courtesy of Jason Ware; Charles Liu: courtesy of
AMNH.
See those teardrop shapes? They are gas and dust clouds that cradle infant stars. Most stars form
in tightly packed groups called star clusters.
© AMNH
The Pleiades is an older star cluster than the one in Orion. Young stars are leaving this cluster,
too.
© AMNH
Scientists also observe stars at the ends of their lives. The remains of one of these stars formed
the Helix Nebula.
© AMNH
All that remains of the star is a very dense object called a white dwarf. It will take billions of years
to cool and slowly fade away.
© AMNH
Brown dwarfs are neither stars nor planets. And they are as numerous as stars! The discovery
of these new objects tells us that our cosmic family is more diverse than we imagined.