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With a telescope, you can see thousands of stars. Stars
are giant balls of gas that use up hydrogen when they shine. When they run out of
hydrogen, they can use other elements. Eventually, their fuel supply runs out
and they die.
Stars are often found in clusters, hundreds together.
The famous star cluster called The Pleiades is shown at the right.
Sometimes (as in the Pleiades picture) stars appear to have bright
spikes or crosses through them. These aren't really part of the star - they're just
an optical illusion that comes from the telescope.
Nebulae (the plural of nebula) are places where new stars are born.
They are collections of gas and dust that come together due to gravity to form stars.
Galaxies are huge collections of stars. Our galaxy, The Milky Way,
may contain up to a trillion stars. No one is exactly sure
how many. Other galaxies are even bigger. Some "dwarf"
galaxies are much smaller.
Galaxies come in different shapes. The three types of galaxies
are spiral, elliptical, and irregular. Examples of each type are
shown below.
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Elliptical
galaxy |
Spiral
galaxy
(seen from the front) |
Spiral
galaxy
(seen from the side) |
Irregular galaxy |
Galaxies come in clusters, just like stars do. Some galaxies are so
far away that they look like stars. Sometimes, galaxies pass close to each other. When they do, their
gravity can cause them to warp. The galaxies can
bend each other, making them look like the pair shown below.
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A close pair of
galaxies |
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Quasar
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Quasars are galaxies with active centers. They are so far away
that they look like stars. They are very far away but they shine brightly: one
quasar can be as bright as millions of regular galaxies. The red "star" shown to
the right is actually a quasar.
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