Galaxy, Solar System and Planets
Galaxy,
Milky
Way, Stars,
Solar
System, Asteroids,
Sun,
Comet,
Natural
Satellite, Moon
Nine planets: Mercury,
Venus,
Earth,
Mars,
Jupiter,
Saturn,
Uranus,
Neptune
and Pluto
| Galaxy:
Hundreds of millions of stars, all gravitationally interacting,
and orbiting about a common center. Astronomers estimate that there
are about 125 billion galaxies in the universe. All the stars visible
from the Earth belong to Earth’s galaxy called the Milky Way.
The Sun, with its associated planets, is just one star in this galaxy.
Besides stars and planets, galaxies contain clusters of stars; atomic
hydrogen gas; molecular hydrogen; complex molecules composed of
hydrogen, nitrogen, carbon, and silicon, among others and cosmic
rays. |
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| Milky
Way: the large, disk-shaped aggregation of stars, or galaxy,
that includes the Sun and its solar system. In addition to the Sun,
the Milky Way contains about 400 billion other stars. There are
hundreds of billions of other galaxies in the universe, some of
which are much larger and contain many more stars than the Milky
Way. |
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| Stars:
Massive shining sphere of hot gas. Of all the stars in the Universe,
our Sun is the nearest to Earth and the most extensively studied.
The stars visible from the earth all belong to the Milky Way Galaxy,
the massive ensemble of stars that contains our solar system (the
Sun and it’s nine planets). |
| Solar
System: The Sun and the celestial bodies orbiting the Sun.
Including the nine planets and their satellites; the asteroids and
comets; and interplanetary dust and gas. Here the solar system refers
to the system that includes Earth and the Sun. |
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| Asteroids:
one of the many small or minor rocky planetoids that are members
of the solar system and that move in elliptical orbits primarily
between the orbits of Mars and Jupiter. |
Sun:
closest star to Earth. The Sun is a huge mass of hot, glowing
gas. The strong gravitational pull of the Sun holds Earth and
the other planets in the Solar System in orbit. The Sun’s
light and heat influence all of the objects in the solar system
and allow life to exist on Earth. Sun light is a combination of
seven colors called rainbow. |
| Comet:
relatively small, icy celestial body revolving around the Sun. When
a comet nears the Sun, some of the ice in the comet turns into gas.
The gas and loose dust freed from the ice create a long, luminous
tail that streams behind the comet. |
Natural
Satellite: in astronomy, a celestial body that orbits a
larger celestial body. The larger body is referred to as the satellite’s
primary. Natural satellites that orbit planets are often called
moons.
The best-known natural satellite is Earth's Moon. The Moon is unusually
large relative to the size of its primary (Earth); in fact, it is
significantly larger than the planet Pluto. The Moon’s surface,
like the surfaces of most of the natural satellites in the solar
system, is heavily cratered and geologically inactive. |
| Moon:
Name given to the only natural satellite of Earth. The Moon is the
second brightest object in Earth’s sky, after the Sun, and
has accordingly been an object of wonder and speculation for people
since earliest times. The natural satellites of the other planets
in the solar system are also sometimes referred to as moons |
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| Nine planets:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and
Pluto. |
| Mercury:
Orbits closest to the Sun. |
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| Venus:
The second in distance from the Sun. |
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| Earth:
The only planet known has a life, and the “home” of
human beings. From space Earth resembles a big blue marble with
swirling white clouds floating above blue oceans. About 71 percent
of Earth’s surface is covered with water, which is essential
to life. The rest is land, mostly in the form of continents that
rise above the oceans. |
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| Mars:
It is the fourth planet from the Sun. |
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| Jupiter:
Fifth planet from the Sun and the largest planet in the solar System.
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| Saturn:
Sixth planet in order of distance from the Sun, and the second largest
in the Solar System. |
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| Uranus:
Major planet in the solar system, seventh planet from the Sun. Uranus
revolves outside the orbit of Saturn and inside the orbit of Neptune.
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| Neptune:
It is an eight planet from the Sun and fourth largest in diameter.
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| Pluto:
Ninth planet from the Sun and outermost known planet of the Solar
System. |
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