Extrasolar PlanetsBrian JacksonPtyS206, Section 22008 May 1What are “extrasolar planets”?• Extrasolar means outside of our solar system. These are planets that are in other solar systems.• They orbit stars other than our Sun.• Extrasolar planets are fairly close to us and lie within our Galaxy (can’t detect planets in other galaxies)• Is there life in these extrasolar systems?First Extrasolar Planet Found: 51 Peg bFirst Extrasolar System with Many Planets: upsilon AndromedaHow do we find extrasolar planets?• Doppler wobble– http://www.howstuffworks.com/planet-hunting2.htm• Transit signature– Same website• One problem is that it’s hard to detect Earth-like planets because they’re so small Hard to find life?How are extrasolar planets different from our planets?• Many extrasolar planets have orbits that are very non-circular.– Why is our solar system different?• Many big extrasolar planets are very close to their sun.– Closest planet is HD 41004 Bb, almost thirty times closer to its sun than Mercury but planet is more than 10,000 times more massive than Mercury!Eccentric OrbitsPlanets very Close to Star: GJ 876 dWhy are extrasolar orbits so non-circular? • No one really knows!• Maybe multiple planets in system interact and throw some of the planets out of the system (planet-planet scattering).Planet-Planet Scattering: ups AndPlanet-Planet Scattering: animation• http://www.astro.northwestern.edu/rasio/UpsAndPR/JPG/UpsAnd.movNow what about these close-in planets?• How do planets get so close to their suns?– Planet-Planet Scattering?• Are these planet subject to unusual effects?– Mass loss – very strong sunlight makes some of the planet’s mass evaporate away – Tides – Because planets are so close, star can raise big tides on the planetsTidesWhat are the effects of tides?Cracks in Europa’s surfaceWhat are the effects of tides?Volcanoes! http://photojournal.jpl.nasa.gov/archive/PIA09357.movWhat about volcanoes on
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