Distinguish between celestial bodies and give examples. Interpret data to compare various celestial bodies.
Our solar system includes the Sun and all the objects that orbit it due to its gravity, including the Earth.
A celestial body is any natural body outside of the Earth’s atmosphere. There are various celestial bodies, including planets, stars, moons, comets and asteroids.
Planets
A planet is an object that: zz
zz zz
Has enough gravity to clear the space debris (waste) in its orbit.
Moons
A moon is a natural satellite which orbits a planet.
The Earth’s moon is simply called the Moon. The moons of other planets in the solar system have been given names. For example, Titan is a moon of Saturn.
z
Object Type of object Relative mass Relative radius Planet
Earth
Ganymede Moon of Jupiter Moon of Saturn Moon of Jupiter Moon of Jupiter Moon of Earth Moon of Jupiter Moon of Neptune
Titan
Callisto Io
Moon
Europa Triton
368 368 1
0.0248 0.0225 0.0180 0.0150 0.0123
0.00803 0.00359
1
0.413 0.404 0.378 0.286 0.273 0.245 0.212
Fig. 21.2.1 Titan, one of Saturn’s moons
The table below shows the features of some moons compared to the Earth. Relative
surface gravity 1
0.15 0.14
0.126 0.183 0.166 0.134
0.0797
Composition of atmosphere
Nitrogen and oxygen Oxygen
Nitrogen and methane Carbon dioxide Sulfur dioxide No atmosphere Oxygen
