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Unit 3 Lesson 5
Unit 3 Lesson 4
Term | Definition |
---|---|
Terrestrial planet | A planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system. |
Astronomical unit | A unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun. |
Prograde | Having a rotational or orbital movement that is the same as most bodies within a celestial system. |
Retrograde rotation | Retrograde motion is motion in the direction opposite to the movement of something else and the contrary of direct or prograde motion. |
Planetary ring | A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in a flat disc-shaped region. |
Dwarf planet | A celestial body resembling a small planet but lacking certain technical criteria that are required for it to be classed as such. |
Kuiper belt | A region of the solar system beyond the orbit of Neptune, believed to contain many comets, asteroids, and other small bodies made largely of ice. |
Gas giant | A large planet of relatively low density consisting predominantly of hydrogen and helium, such as Jupiter, Saturn, Uranus, or Neptune. |