Exploring the Cosmos

absorption lines appear astronomers atmosphere atom axis binary black hole body bright carbon celestial centimeter chemical chromosphere clusters of galaxies comet constellation core corona cosmic cosmological craters diameter disk distance dust earth electromagnetic electron elliptical emission emitted energy evolution Galactic globular clusters gravitational H-R diagram helium Hubble hydrogen infrared interstellar clouds interstellar medium kilometers per second luminosity lunar magnetic field magnitude main sequence Mars mass matter Mercury Milky molecules moon motion nebula nucleus objects Observatory observed open clusters orbit particles percent photograph photons photosphere planetary quasars radiation radio radius rays red giants redshifts regions relative ring rotation satellites shown in Figure solar system space spectral spectral classes spectrum sphere spiral arms spiral galaxies star's stellar structure sun's sunspot superclusters supergiants supernova surface telescope temperature terrestrial planets thermal tion ultraviolet universe Uranus velocity Venus visible wavelength waves white dwarf X-ray