Astronomy DSST Study Questions and Answers

Planets Small, non luminous bodies that shine by reflected light. Star A self-luminous ball of hot gas that generates its own energy. Sun 109 x5 larger than Earth. AU Distance from the Earth to the Sun. Astronomical Unit (AU) 1.5 x 10"m Light year Distance light travels in a year. 63,000 AU (10[13]km) Galaxy Cloud of stars, gas and dust and bound by gravity of all the matter. Can range from 1500, to 300,000 light years and can contain over 100 billion stars. Milky Way 75,000 light years in diameter. In 1928, International Astronomical Union Established 88 official constellations. Asterism Less formally defined groupings of stars. (ex. Big dipper part of Great Bear). John Bayer 1603 published Uronometria atlas of sky used lower case Greek Letters by brightness. Magnitude Scale Six classes of stars (brightest1-7 fastest 6). Hipparches Compiled first star catalog. Zenith Top of sky above our heads. Nadir Bottom of sky beneath our feet. North Celestial pole Above north pole. South Celestial pole Above south pole. Celestial equator Halfway between poles.