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Download Extrasolar planets
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First direct image of extrasolar planets 10.7 billion miles Fomalhaut A is 16 times brighter than the Sun and is 200 million years old. The planet has a mass of 3 Jupiter’s masses and orbital period 872 years. It is too bright for its size and is probably still contracting, or has a ring. We know there should be planets around other stars. How to find them??? Star-Birth Clouds in M16 (Eagle Nebula). J. Hester and P. Scowon (Arizona St. Univ.), November 2, 1995. Taken with NASA Hubble Space Telescope, WFPC2 M > 2000 M JUPITER SHINES WEAKER THAN THE SUN: 1 000 000 000 TIMES 50 000 TIMES 5 000 TIMES (visible light) (infrared) (mm and sub-mm) JUPITER OBSERVED FROM THE NEAREST STAR 0.1” DISTANT FROM THE SUN „DROWNED” IN SUNSHINE !! POPULAR VIEW REALITY X = CENTER OF MASS SYSTEM VIEWED POLE-ON (RARE) Center of Mass (SLIDESHOW MODE ONLY) THE PLANET CANNOT BE SEEN ...BUT MOTIONS OF THE STAR BETRAY ITS PRESENCE ! 450 km 9 cm/s 150 000 000 km 30 km/s X EARTH 750 000 km 13 m/s JUPITER X 780 000 000 km 13 km/s MOTIONS OF THE SUN VIEWED FROM A STAR 30 LIGHT YEARS AWAY 2020 1995 2010 1990 0.002’’ IS THE ANGULAR SIZE OF A MAN ON THE MOON OR A STANDARD NEWSPAPER FONT 300 KM AWAY 2015 2000 0.002” Unobservable! 2005 STELLAR WOBBLE RECEDING: REDDER APPROACHING: BLUER The Doppler Effect The light of a moving source is blue/red shifted by Dl/l0 = vr/c l0 = actual wavelength emitted by the source Blue Shift (to higher frequencies) vr Red Shift (to lower frequencies) Dl = Wavelength change due to Doppler effect vr = radial velocity 1 Angstrom = 10-8 cm PLANET DETECTION DUE TO STELLAR WOBBLE 100 m/s P normal to the orbit i to the observer 50 K 0 V -50 -100 0 1 2 days 3 K = Vsin i Only the function of masses and inclination angle can be measured ANOTHER EFFECT: TRANSIT PLANET IN FRONT OF THE STAR TRANSIT BRIGHTNESS LIGHT CURVE 1% TIME Measure the radius of the planet, know the mass -> find the mean density!! First direct detection of radiation from extrasolar planet! Spitzer Infrared Telescope First detection of any carbon-bearing molecule on a planet outside the Solar System! Swain et al., Nature, March 2008 Also confirmed previous discovery of water on this planet 326 extrasolar planets are found so far http://planetquest.jpl.nasa.gov/ Planetary system of u And 0.85 AU 242 days 2 MJ 0.06 AU 4.5 days 0.75 MJ 0.39 AU 89 days 0.73 AU 228 days 1 AU 1 year 2.5 AU 3.5 years 4 MJ 1.54 AU 1.9 years Solar system Source: Harvard-Smithsonian CfA Are we alone in the Universe?? Are there any Earth-like planets in habitable zones around stars? Habitable zones April 25, 2007: Discovery of the first Earth-like planet in the habitable zone!! Red dwarf What would be the signs of life on other planets?? Signs of life in the spectrum: