AST101H1 Lecture Notes - Lecture 1: Milky Way, Astronomical Unit, Local Group
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AST101H1 Full Course Notes
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Solar system is the sun, planets and all their moons: a star and all the objects that orbit it. Universe is the totality of all space, time, energy and matter. Our cosmic address": our planet (earth, our solar system (solar system, our galaxy (milky way galaxy, our galaxy cluster (local group, the universe (universe) Galaxy: a great island of stars in space, containing millions, billions, or even trillions of stars: all held together by gravity and orbiting a common center. Sun and earth are 150,000,000,000 m apart: 1. 5 x 1011m, 1au (astronomical unit) Maximum possible separation between earth and mars is 2. 5 au. A light year is a measure of distance (the distance that light travels in year: nearest star is 4. 4ly (light years) away. 1 au = 8. 3 light minutes the sun is 8. 3 light minutes from earth. Star: balls of plasma which produce energy by nuclear fusion.