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10 Cards in this Set

  • Front
  • Back
astronomical unit (AU)
Average distance from Earth to the sun; 1.5 x 108 km, or 93 x 106 mi. (p. 6)
A large system of stars, star clusters, gas, dust, and nebulae orbiting a common center of mass. (p. 8)
light-year (ly)
A unit of distance. The distance light travels in 1 year. (p. 7)
Milky Way
The hazy band of light that circles our sky. Produced by the glow of our galaxy. (p. 8)
Milky Way Galaxy
The spiral galaxy containing our sun. Visible in the night sky as the Milky Way. (p. 8)
A small, nonluminous body formed by accretion in a disk around a protostar. (p. 6)
scientific notation
The system of recording very large or very small numbers by using powers of 10. (p. 6)
solar system
The sun and its planets, asteroids, comets, and so on. (p. 6)
spiral arm
Long spiral pattern of bright stars, star clusters, gas, and dust. Spiral arms extend from the center to the edge of the disk of spiral galaxies. (p. 8)
A globe of gas held together by its own gravity and supported by the internal pressure of its hot gases, which generate energy by nuclear fusion. (p. 6)