Astronomy 311: Extra-Solar Planets• An extraterrestrial astronomer surveying our solar system with the Dopplertechnique could discover the existence of Jupiter with just a few days ofobservations.• The fact that we have not discovered an Earth-mass planet tells us thatsuch planets must be very rare.• Within the next few years, astronomers expect to confirm all the planetdetections made with the Doppler technique by observing transits of thesesame planets.• Although ”hot Jupiters” ar e unlikely places to find life, they could be or-bited by moons that would have Earth-like temperatures.• Before the discovery of planetary migration, scientists were unable to ex-plain how Saturn could have got to its current o r bit.• Next year, astronomers will be able to use the Doppler technique to findEarth-like planets.• In 2025, astronomers will obtain a spectrum showing the presence of oxygenin the a t mosphere of an Earth-like planet,• In 204 0, we will be able to journey to an extra-solar planet.• An extrasolar planet is discovered with an orbital period of 3 days.• The number of extrasolar planets discovered by 2010 will be about 1000.• Each second the Sun emits 1026W = 1026J/ s. What fraction of that energyis received by the Earth every second assuming the radius of the Earth is6400km? If the earth’s reflectivity is 0.29, how would your answer change?• So would it be easy/hard to detect a planet by searching for reflected sun-light?• For a planetary transit, the fraction of light blocked by the transiting planetisP lanet0sdiskareaStar0sdiskarea=πr2planetπr2star,sorplanet≈ rstar×qfractionoflightblocked.• If a planetary tr ansit blocks 2% of the host star’s light which has a radiusof a bout 85% of t he Sun’s radius.1• Conservation of momentumMstarvstar= Mplanetvplanet,relative to the center of mass of the system. ThenMplanet= Mstarvstarvplanet.If the planet moves in a roughly circular orbit, an expression for vplanetisvplanet=2πaplanetpplanet,soMplanet= Mstarvstarpplanet2πaplanet.• If the smallest velocity measurement is 1 m/s what is the least massiveplanet that can be detected at 0.1AU from a 1 solar mass star? How aboutat a distance of
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