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Download GS Astro Part VIII - Hamburger Sternwarte
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Das moderne Universum Prof. Dr. Jochen Liske Hamburger Sternwarte [email protected] www.hs.uni-hamburg.de/liske Das moderne Universum Teil VIII: Extrasolare Planeten Definition Planet Definition Planet Definition der Internationalen Astronomischen Union (2006): The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way: 1. A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. 2. A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. 3. All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". Credit: ESO Definition Extrasolarer Planet Emphasizing again that this is only a working definition, subject to change as we learn more about the census of low-mass companions, the Working Group on Extrasolar Planets (WGESP) has agreed to the following statements: 1. Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System. 2. Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located. 3. Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "subbrown dwarfs" (or whatever name is most appropriate). These statements are a compromise between definitions based purely on the deuterium-burning mass or on the formation mechanism, and as such do not fully satisfy anyone on the WGESP. However, the WGESP agrees that these statements constitute the basis for a reasonable working definition of a "planet" at this time. We can expect this definition to evolve as our knowledge improves. Dale Frail Aleksander Wolszczan Credit: ESO Didier Queloz Michel Mayor Credit: ESO Credit: ESO Credit: ESO Credit: ESO Credit: ESO Credit: ESO / Geneva Observatory Credit: ESO Credit: NASA / Kepler Credit: NASA / Kepler Credit: ESO Credit: ESO Credit: ESO / A.-M. Lagrange Credit: ESO / A.-M. Lagrange Credit: NRC-HIA / C. Marois / Keck Observatory Stand 02. 12. 2015 Fast jeder Stern ist von mindestens einem Planeten umgeben. Ca. 20% sonnenähnlicher Sterne haben einen erdähnlichen Planeten in der bewohnbaren Zone. http://exoplanetarchive.ipac.caltech.edu http://planetquest.jpl.nasa.gov http://exoplanet.eu Credit: ESO Credit: Alex Parker Credit: Daniel Fabrycky Credit: ESO Credit: NASA Ames / JPL-CalTech / R. Hurt Credit: NASA Ames / JPL-Caltech / T. Pyle & W. Stenzel Credit: ESO Credit: ESO Credit: NASA / Kepler Venus Erde Mars Credit: ESA
