f10_oct21 - Ast 307 - Oct. 21 , 2010 Extrasolar Planets and...

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Unformatted text preview: Ast 307 - Oct. 21 , 2010 Extrasolar Planets and Planetary Systems Molecules in Planetary Atmospheres The molecules in the atmospheres of the terrestrial planets may provide information on biological activity; but obtaining such spectra will be challenging On the other hand, some such molecules have now been seen in giant transiting planets Molecules in Transiting Exoplanets Water (H 2 O) and methane (CH 4 ) have been detected in the transiting planet HD 187933b; CO might be present as well. Microlensing Method There is another method which relies on changes in the brightness of a star (but not the star the planet orbits!) This method is based on the prediction from Einsteins theory of gravity, General Relativity, that the presence of matter will bend the path of a ray of light. When looking towards a background star, if another star (with a planet) moves nearly in front of it, we see a brightening effect, as if a magnifying glass were being passed in front of it. Exoplanets: Timing Method Found in pulsars: the star is displaced along the line of sight (forward and back) due to presence of a planet This causes a delay in the arrival time of the pulses due to the extra distance the light (or radio wave) must travel The first claim of detection of planets around a pulsar, made by A. Lyne in 1991, was bogus. The period was exactly 1 year; he was seeing the effect of Earths orbit! Exoplanets: Timing Method Soon afterwards, however, Andrew Wolszczan found definite evidence of multiple, low-mass objects orbiting the pulsar B1257+12.- he found two planets of about 4 Earth masses each, in orbits with a = 0.37 and 0.47 A.U.- proof of their reality? You can see them tug on each other, affecting their orbits Pulsar B1620-26 in the globular cluster M4 appears to have a ! 10 Jupiter mass object orbiting it; this is a binary pulsar in which a disk was formed, due to mass transfer. Planet Discoveries by U.T. Researchers Hobby-Eberly Telescope, McDonald Observatory First HET Planet!...
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f10_oct21 - Ast 307 - Oct. 21 , 2010 Extrasolar Planets and...

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