 | Term | Definition |
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solary system |
system of nine planets, including Earth, and other objects that revolve around the Sun |
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Mercury |
2nd smallest planet, closest to the Sun; does not have a true atmosphere; has a surface with many craters and high cliffs |
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Venus |
second planet from the Sun; similar to Earth in mass and size; has a thick atmosphere and a surface with craters, faultlike cracks, and volcanoes |
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Earth |
third planet from the Sun; has an atmosphere that protects life and surface temperatures that allow water to exist as a solid, liquid, and gas |
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Mars |
fourth planet from the Sun; has polar ice caps, a thin atmosphere, and a reddish appearance caused by iron oxide in weathered rocks and soil |
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Jupiter |
largest and fifth planet from the Sun; contains more mass than all the other planets combined, has continuous storms of high-pressure gas, and an atmosphere mostly of hydrogen and helium |
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Great Red Spot |
giant, high-pressure storm in Jupiter's atmosphere |
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Saturn |
second-largest and sixth planet from the Sun; has a complex ring system, at least 31 moons, and a thick atmosphere made mostly of hydrogen and helium |
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Uranus |
seventh planet from the Sun; is large and gaseous, has a distinct bluish-green color, and rotates on an axis nearly parallel to the plane of its orbit |
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Neptune |
usually the eighth planet from the Sun; is large and gaseous, has rings that vary in thickness, and is bluish-green in color |
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Pluto |
considered to be the ninth planet from the Sun; has a solid icy-rock surface and a single moon, Charon |
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comet |
space object made of dust and rock particles mixed with frozen water, methane, and ammonia that forms a bright coma as it approaches the Sun |
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meteor |
a meteoroid that burns up in Earth's atmosphere |
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meteorite |
a meteoroid that strikes the surface of a moon or planet |
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asteroid |
a piece of rock or metal made up of material similar to that which formed the planets; mostly found in the asteroid belt between the orbits of Mars and Jupiter |
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photosphere |
lowest layer of the Sun's atmosphere; gives off light and has temperatures of about 6,000K |
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chromosphere |
layer of the Sun's atmosphere above the photosphere |
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corona |
outermost, largest layer of the Sun's atmosphere; extends millions of kilometers into space and has temperatures up to 2 million K |
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sunspots |
areas on the Sun's surface that are cooler and less bright than surrounding areas, are caused by the Sun's magnetic field, and occur in cycles |
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nebula |
large cloud of gas and dust that contracts under gravitational force and breaks apart into smaller pieces, each of which might collapse to form a star |
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giant |
late stage in the life of comparatively low-mass main sequence star in which hydrogen in the core is deleted, the core contracts and temperatures inside the star increase, causing its outer layers to expand and cool |
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white dwarf |
late stage in the life cycle of a comparatively low-mass main sequence star; formed when its core depletes its helium and its outer layers escape into space, leaving behind a hot, dense core |
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supergiant |
late stage in the life cycle of a massive star in which the core heats up, heavy elements form by fusion, and the star expands; can eventually explode to form a supernova |
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neutron star |
collapsed core fo a supernova that can shrink to about 20 km in diameter and contains only neutrons in the dense core |
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black hole |
final stage in the evolution of a very massive star, where the core's mass collapses to a point that its gravity is so strong that not even light can escape |
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galaxy |
large group of stars, dust, and gas held together by gravity; can be elliptical, spiral, or irregular |
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