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stars planets

means "wanderers" in Greek


In 17th Century, he used the telescope to study the planets and stars

solar system

includes the sun, the planets, and many smaller objects

Saturn System

made up of the planet Saturn and the several moons that orbit Saturn

astonomical unit

average distance between the Earth and the sun; approximately 150 million kilometers (AU)

eight bodies

Until the 17th Century, the universe was throught to hae only ____________.

inner solar system

contains four planets that are closest to the sun.

outer solar system

contains the planets that are farthest from the sun

terrestrial planets

inner planets that have dense and rocky surfaces

Gas giants

planets that have deep, massive atmosheres rather than hard rocky sufaces. Jupiter, Saturn, Uranus, and Neptune


The only planet of the outer solar system that is small, dense, and rocky.

18th Century

This is when the plant Uranus was discovered


invention that helped early scientists discover more bodies in the solar system


on this planet, you would only weigh 38% of what you weigh on Earth and a day on this planet would take 59 Earth days.

period of rotation

the amount of time that an object takes to rotate once


the time that a planet takes to go around the sun once


the motion of a body orbiting another body in space

period of revolution

the time an object takes to revolve around the sun once


This planet is more like the Earth than any other planet; it is smaller, less massive and less dense than Earth.

prograde rotation

appears to spin in a counterclockwise direction when it is viewed from above the North Pole

retrograde rotation

a planet that spins in a clockwise direction

greenhouse effect

carbon dioxide traps thermal energy from sunlight in this process


Venus has the ________ surface of any planet in the solar system (464 degrees).


a spacecraft that mapped the surface of Venus using radar waves in 1990-1992


Venus, like Earth, has ________________.


National Aeronautics and Space Administration

right distance from the sun

_________________ allowed Earth to prevent water from freezing or from boiling away


Perhaps the most studied planet in the solar system (other than Earth)


Mars is a (cold or hot) planet

Viking I & Viking 2

These landed on Mars in 1976 and Mars Pathfinder landed on Mars in 1997.

Olympus Mons

A large mountain with an extinct shield volcano on Mars


Largest planet in our solar system. Made up of hydrogen and helium

Great Red Spot

a storm system that is ore than 400 years old on Jupiter


2nd largest planet in the solar system. This planet has rings and is still forming


icy particles that range in size from a few centimeters to several meters -- usually surround gas giants


discovered by English amateur astronomer William Herschel in 1781, this planet is tipped over on its side


discovered in 1846, this planet has belts of clouds in its atmosphere


sometimes called the mystery planet, this is the farthest planet from the sun and the smallest planet


Pluto's moon, which is more than half its size


natural or artificial bodies that revolve around larger bodies such as planets


Except for Mercury and Venus, all planets have natural satellites called ______


another name for the Earth's moon

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