AST201H1 Lecture Notes - Interstellar Cloud, Ballpoint Pen, Solar System
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AST201H1 Full Course Notes
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Sun will expand, engulf the earth and destroy everything on the planet (in about 4. 5 million yrs. ) Stars - hydrogen + helium with nuclear fusion at the centre; have own source of energy (unlike a planet: different telescopes allows different ways to see universe. Planets - orbit a star; can be rocky, icy or gassy in composition; don"t produce much energy. In 2006 the international astronomical union accepted a new definition of the term planet": 1. Planets orbit a star (not another planet: 2, 3. Pluto is not a planet because its orbit is full of other stuff (mainly comets) If sun is grapefruit, earth is tip of ballpoint pen. Solar system is huge and vast majority is empty". 1au = astronomical unity, the average distance between earth and sun. 1 light year is the distance light travels in one year. Lecture 1 - our place in the universe.