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Beyond the Solar System
By Patti Hutchison
Caption: Barred spiral galaxy NGC 1300 photographed by Hubble
telescope.
Our solar system extends billions of miles from Earth. But there is
still something bigger. It is the Milky Way, our galaxy. But wait,
there's something even bigger than that- the universe!
There are billions of galaxies in space. A galaxy is a group of stars,
gas, and dust that are bound together by gravity. If you look into the
sky on a dark night, you can see our galaxy, the Milky Way. It is a
shimmering belt that stretches across the sky. The Milky Way contains the solar system we live in.
The smallest galaxies contain only a few hundred thousand stars. The largest can contain trillions of stars.
Galaxies bump into each other every so often. The Milky Way has had other galaxies pass through it. But there
is no danger; the stars are so far apart that a collision is not likely to happen.
Galaxies come in different shapes. There are spiral, elliptical, lenticular, and irregular shapes. About half the
galaxies in the universe are spiral galaxies. A spiral galaxy looks like a twirling octopus. In the "arms" of the
galaxy, new stars are formed. Some of them are very large. They cause the surrounding clouds of dust to glow
brightly, also. Spiral galaxies are beautiful to see.
New stars are not formed in elliptical galaxies. The stars in them were formed many years ago. They are
often close together, making the middle of the galaxy glow very brightly. If there were any planets in an elliptical
galaxy, it would never be night. The sky would be bright all the time.
Lenticular galaxies are shaped like a lens. They have ripples like a spiral galaxy but are more flattened. Like
elliptical galaxies, lenticular galaxies have older stars in them. The stars are spread out evenly.
Any galaxy that is not spiral, elliptical, or lenticular is said to be irregular. Irregular galaxies come in many
shapes and sizes. They have very little organization. Scientists think some galaxies are irregular because some
event has disturbed them. Others just lack the organization and the rotation of a spiral galaxy.
The universe is made up of billions of galaxies. The galaxies cluster together in groups. If you could look at
the whole universe at once, it would look like a spider web. Between the galaxies, space is almost completely
empty. Tiny atoms are hundreds of miles apart.
No one knows how big the universe actually is. Scientists are constantly trying to measure it. They do know,
however, that it is expanding all the time. Space missions travel farther and farther into space. Will they find life
somewhere else in the universe?
Name
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Beyond the Solar System
Questions
1. What is a galaxy?
2. Other galaxies have passed through the Milky Way.
A. false
B. true
3. A galaxy with twirling arms is called:
A. a spiral galaxy
B. an elliptical galaxy
C. a lenticular galaxy
4. Where are new stars formed?
A. neither a nor b
B. in an elliptical galaxy
C. in the arms of a spiral galaxy
5. What kind of galaxy does not form new stars?
A. irregular
B. spiral
C. elliptical
6. What is the space between galaxies like in the universe?
Write a paragraph about the relationships between the solar system, the Milky Way, and the universe.
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Do you think there is life in other galaxies? Write a paragraph giving reasons for your opinion.