a model of the universe in which Earth is at the center of the revolving planets and stars
a model of the solar system in which Earth and the other planets revolve around the sun
an oval shape which may be elongated or nearly circular; the shape of the planets' orbits
the central region of the sun, where nuclear fusion takes place
the process by which hydrogen atoms join together in the sun's core to form helium
a region of very tightly packed gas in the sun's interior where energy is transferred mainly in the form of light
the outermost layer of the sun's interior
the inner layer of the sun's atmosphere that gives off its visible light
the middle layer of the sun's atmosphere
the outer layer of the sun's atmosphere
a stream of electrically charged particles that eminate from the sun's corona
a dark area of gas on the sun's surface that is cooler than surrounding gases
a huge reddish loop of gas that protrudes from the sun's surface linking parts of sunspot regions
an eruption of gas from the sun's surface that occurs when the loops in sunspot regions suddenly connect
the name often given to the four inner planets: Mercury, Venus, Earth, and Mars
the trapping of heat by a planet's atmosphere
the name often given to the first four outer planets: Jupiter, Saturn, Uranus, and Neptune
a thin disk of small ice and rock particles surrounding a planet
a loose collection of ice, dust, and small rocky particles, typically with a long, narrow orbit
the fuzzy outer layer of a comet
the solid inner core of a comet
a doughnut shaped region that stretches from around Pluto's orbit to about 100 times Earth's distance from the sun
a spherical region of comets that surrounds the solar system
rocky object revolving around the sun that are too small and numerous to be considered planets
the region of the solar system between the orbits of Mars and Jupiter where many asteroids are found
a chunk of rock or dust in space
a streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere
a meteoroid that passes through the atmosphere and hits Earth's surface
life that exists other than on Earth
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