Extra-Solar Planets
•Hard to see faint planet right next to very bright star
•Two indirect techniques available
(Like a binary star system but where 2nd “star” has extremely low mass)
–Watch for Doppler “wobble” in position/spectrum of star
–Watch for “transit” of planet which slightly dims light from star
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•About 230 planets discovered since 1996   See http://exoplanets.org/
•Tend to be big (³Jupiter) and very close to star    (easier to see)
From our text: Horizons, by Seeds
51 Peg – the first extra-solar planet discovered
HD 209458 – Transit of planet across star