AST MARCH 26.docx

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Astronomy & Astrophysics
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Susan Pfieffer

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AST251 MARCH 26 2012 LECTURE 11 INTRODEPEND ON WHAT WE CAN SEE WHAT WE SEE NOT BE REP OF ENTIRE PPLANETS THIS CALLED SELECTION BIAS Main sequMost of time on main sequence Burn h in heMain sequence all related mass surface temp lum and shorter the lifetime More fuel to burn live shorter G is the sun Bottom 3 low lumoinoaity cool starsTop 3 high lum hot stars1 percent or million times more luminous then the sun PropertiesLife time Is op big stars die quicly very small stars live almost forevcer 100s of billions of yearsOb die to quick life on earth 100 my to develop3 percent on a and f So low mass region long life times many stars in these categories sun is a g star know one planet around g starStars coolerLuminosity temp goes downBottom line is less lum stars habitable zone closer to the sun such to support liquid water Earth quite in inner edge of habitable zone venus and mercry in and mars on outer this is gFir k mercury goodFor m mercury would be too far awayMmons of Jupiter show same face tidal locking closer planet is to star more likely tidally locked on side always faces star another doesnt whether good for life or not is unknownMuch coolerLower mass brown dwardfs so small not heat up in center to start nuclear burning just h balls larger versions of Jupiter circles brown dwarfs below 08 solar masses no chance for lifeLower surface temp less lumBinary starsSun exceptional is that its alone
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