Introductory Astronomy

angle angular Apollo 11 appear asteroids astronomical atom axis barycenter binary bright calendar called celestial bodies celestial equator Cepheid clouds comet constellation craters dark density diameter disk distance earth earth's atmosphere earth's surface eclipse ecliptic electrons emitted energy equinox Explain focal galactic Globular cluster gravitational H-R diagram Hale Observatories horizon hydrogen increase interstellar Jupiter latitude light curve located luminosity lunar magnetic field magnitude main-sequence Mars mass maximum meridian meteor meteorite miles Milky moon moon's motion move nebula nucleus observed observer's occur Open cluster parallax parsecs particles passes period photograph planet planetary planetary nebulae Plate polar pole position produced radiation radio refraction region revolves rotation satellites sidereal sidereal period solar system space spectral class spectral lines spectrum speed sphere spherical star star's stellar sun's sunspot synodic period telescope temperature tion universe Uranus variable Venus visible wavelength waves white dwarf