AST101H1 Lecture 2: AST101 Lecture #2

• School: UTSG
• Department: Astronomy and Astrophysics
• Course: AST101H1
• Professor: Bryan Gaensler, C. Barth Netterfield, Ilana MacDonald

Document Summary

1 au (astronomical unit) = average distance between earth and the sun. 1 ly (light year) = distance light travels in one year, about 63,000 au. Stars are balls of plasma that produce energy by nuclear fusion. Planets are rocky, icy or gassy, and they don"t produce much energy. 3 rules to be a planet: planets orbits stars directly (not other planets, planets must be massive enough for their own gravity to compress them into spherical shapes, cleared their orbit. Pluto is not a planet because its orbit is full of other stuff. Objects that fail the definition of planet are called dwarf planters. Moon is any large body which orbits a planet. Titan is a rocky,icy object with an atmosphere ands liquid on its surface.