AST101H1 Lecture Notes - Lecture 3: Dwarf Planet, Oort Cloud, Gas Giant

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST101H1
• Professor: Michael Reid

Document Summary

Lecture 3 tour of the solar system. Nearest large galaxy to milky way is andromeda: 2. 5 million ly away. Lookback time = how far into the past we are seeing based on how long the light takes to reach us. Stars: balls of plasma which produce energy by nuclear fusion: plasma = hot hot gas, ionized. Planets: rocky, icy, or gassy, and they don"t produce much energy: mainly solids and liquids, planets orbit stars and only planets. In 2006, the international astronomical union (iau) accepted a new definition of the term planet , adding one new criterion to the traditional definition: Planets must be massive enough for their own gravity to compress them into spherical shapes. That is, there can"t be a lot of other stuff orbiting the parent star in orbits very similar to the planet: pluto can"t be a planet because its orbit is full of other objects (mainly comets)