Lecture at July 3

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University of Toronto St. George
Astronomy & Astrophysics
Marija Stankovic

AST201H1S Lecture 1 - Our Place in the Universe July 3/12 The Earth and it’s neighbors • Only planet we know of that has intelligent life • Sun will expand, engulf the earth and destroy everything on the planet (in about 4.5 million yrs.) • Astar of the sun’s size lives about 10 billion years • Winds that sun/star blows are very powerful and dangerous Radiation from near star explosions very harmful to life on earth • • We are connected to the universe; the universe is in us • The universe recycles • New stars form from old stars ABrief Summary of Celestial Objects • 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 • Plasma - very hot gas in stars • Planets - orbit a star; can be rocky, icy or gassy in composition; don’t produce much energy • In 2006 the InternationalAstronomical Union accepted a new definition of the term ‘planet’ • 1. Planets orbit a star (not another planet • 2. • 3. Planets must have a cleared orbit • Pluto is not a planet because its orbit is full of other stuff (mainly comets) • Moon - satellite; a object that orbits a planet • Asteroid - small rocky object orbiting a star • Comet -
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