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Solar System

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081

Solar System

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A solar system is made up of a star and everything that travels around it. Solar means "of the sun." In our Solar System, the Sun is orbited by the terrestrial planets Mercury, Venus, Earth, and Mars, the gas planets Jupiter, Saturn, Uranus, Neptune, and Pluto, and the ring of comets known as the Kuiper Belt. Its outer edge is the spherical cloud of comets called the Oort Cloud.

How Far Out?
Distances in space are so huge that it's hard to imagine how far apart things really are in our Solar System. One way to picture this is to make a scale model. If the Earth is the size of a grape (and you the size of a single atom), the Moon would be about a foot away. At this scale, the Sun is about the height of a man a block away from Earth. Grapefruit-sized Jupiter is five blocks away from the Sun, orange-sized Saturn 10 blocks away, and lemon-sized Uranus and Neptune are, respectively, 20 and 30 blocks away. Even on this scale, you would have to travel 25,000 miles to reach the closest star.

Our Solar System began:

when the planets hatched from the Sun

as a giant spinning cloud of dust and gas

one hundred years ago

Are you right?

Correct!

Our Solar System began as a giant spinning cloud of dust. The Sun formed first, when gravity pulled the gas together. Later, dust and debris orbiting the Sun came together to form the planets.

Our Solar System is held together by:

the force of solar wind

asteroid chains

the Sun's gravity

Are you right?

Correct!

The Sun's gravity is so strong, everything in our Solar System orbits around it. Even comets a light-year out in space are held in orbit by the Sun. The Sun accounts for over 99 percent of all the mass in the Solar System.

We live in the only solar system in the Universe.

Fact
or
Fiction
?

Fiction

Recently scientists have discovered other solar systems, and even young stars with planets beginning to form around them.

Size: about 1.6 light-years across
Boundary: Oort Cloud
Rotation around Sun: counterclockwise
Star size: average
Age: about 4.6 billion years
Contents: terrestrial planets, gas giants, Asteroid Belt, Kuiper Belt, Oort Cloud
Location: in Orion arm of the Milky Way galaxy

Image credits: courtesy of JPL, California Institute of Technology and NASA.