Solar System Exploration and Colonization Vocabulary

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Conversion factor

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A ratio used to convert from one unit to another.

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Dwarf planet

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A celestial body that orbits the sun and has enough mass to assume a nearly round shape but has not cleared its orbital path of other debris.

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Star

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A massive, luminous sphere of plasma held together by gravity, typically emitting light and heat.

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Terrestrial planets

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Planets that are composed primarily of silicate rocks or metals, with a solid surface, such as Earth, Mars, Venus, and Mercury.

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Gas giants

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Large planets that are not primarily composed of rock or other solid matter, such as Jupiter, Saturn, Uranus, and Neptune.

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Map scale

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The ratio of a distance on the map to the corresponding distance on the ground.

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Astronomical unit (AU)

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A unit of measurement equal to the average distance from the Earth to the Sun, approximately 149.6 million kilometers.

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Kilometer (km)

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A unit of length in the metric system, equal to 1,000 meters.

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Atmosphere

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The layer of gases surrounding a planet or other celestial body.

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Solar system

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The collection of eight planets and their moons in orbit around the sun, together with smaller bodies such as asteroids, meteoroids, and comets.