ASTR 100 Lecture Notes - Lecture 1: Milky Way, Terrestrial Planet, Gas Giant

• School: University of Maryland
• Department: Astronomy
• Course: ASTR 100
• Professor: Sylvain Veilleux

Document Summary

Earth is part of the solar system. The solar system is a part of the milky way galaxy. The milky way galaxy is a part of the local group which contains 54 other galaxies. The local group is part of a supercluster of galaxies that are their own galaxy groups. Planets are moderately large objects that orbit a star. A planet shines because light is reflected off of its surface. Planets may be rocky, icy or gaseous in nature. A moon is simply a natural satellite that orbits a planet. Titan, one of the many moons of saturn. Of our 8 planets, 6 have moons orbiting them. There are a total of 178 known natural satellites from these moons. In addition, several moons of dwarf planets also exist. Interestingly, the ratio of the mass of the earth to the mass of the moon is much greater than any other planet-satellite system in the solar system.