ASTR 1000 Lecture Notes - Lecture 1: Interstellar Cloud, Virgo Supercluster, Milky Way
Document Summary
Astronomy = the study of everything in the universe which is beyond the atmosphere of the. Includes: - very large structures (galaxies, clusters of galaxies, the universe itself) very small structures (dust grains, atoms, photons of light) Star = a large, glowing ball of gas that generates heat and light through nuclear fusion. Planet = a moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition. Moon or satellite = an object that orbits a planet. Asteroid = a relatively small and rocky object that orbits a star. Comet = a relatively small and icy object that orbits a star. Solar system = a star and all the material that orbits it, including its planets and moons. Nebula = an interstellar cloud of gas and/or dust. Galaxy = a great island of stars in space, all held together by gravity and orbiting a common center.
