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| the name given to the four planets beyond Mars: Jupiter, Saturn, Uranus, and Neptune; also known as the outer planets; their atmospheres consist mainly of hydrogen and helium gases |
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| Earth-centred; refers to the Earth-centred model of the universe, which places a motionless Earth at the centre with all the planets and stars at fixed positions within eight concentric spheres that spin in circles called orbits |
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| Sun-centred; refers to the Sun-centred model of our solar system, in which all planets revolve around the Sun |
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| Kepler's Laws of Planetary Motion |
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| three laws that state: (1) the planets travel in elliptical orbits around an off-centre Sun, with the Sun at one focal point; (2) the speed of a planet's orbit depends on its distance from the Sun; (3) the farther a planet (or dwarf planet) is from the Sun, the longer its orbit. |
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| Moon's phases, which can be divided into eight distinct stages lunar eclipse results when Earth is positioned between the Sun and the Moon such that Earth casts its shadow on the surface of the Moon |
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| smaller chunk of solid matter that burns up in Earth's atmosphere due to friction, creating a bright streak of light; often called a shooting star |
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| larger meteor that actually reaches Earth's surface |
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| lump of rock or metal that encounters Earth as it travels through space |
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| the non-planetary matter in the solar system; includes asteroids, meteoroids (meteors and meteorites), and comets |
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| a collection of dust and gases, consisting mainly of hydrogen and helium gases and, to a lesser extent, grains of solid matter such as iron, rock, and ice |
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| the points at which the Moon's orbital plane intersects Earth's orbital plane; eclipses occur only at lunar nodes |
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