Evolution Message Board - Msg: 28792621

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Politics : Evolution

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To: Solon who wrote (34439)	3/21/2013 11:14:48 PM
From: Giordano Bruno	Read Replies (1) of 69300

Number of stars with planets Most of the discovered extrasolar planets lie within 300 light years of the Solar System. Planet-search programs have discovered planets orbiting a substantial fraction of the stars they have looked at. However the overall proportion of stars with planets is uncertain because not all planets can yet be detected. The radial-velocity method and the transit method (which between them are responsible for the vast majority of detections) are most sensitive to large planets in small orbits. Thus many known exoplanets are "hot Jupiters": planets of Jovian mass or larger in very small orbits with periods of only a few days. It is now estimated that 1% to 1.5% of sunlike stars possess such a planet, where "sunlike star" refers to any main-sequence star of spectral classes late- F, G, or early- K without a close stellar companion. [67] It is further estimated that 3% to 4.5% of sunlike stars possess a giant planet with an orbital period of 100 days or less, where "giant planet" means a planet of at least 30 Earth masses. [68] The proportion of stars with smaller or more distant planets is less certain. It is known that small planets (of roughly Earth-like mass or somewhat larger) are more common than giant planets. It also appears that there are more planets in large orbits than in small orbits. Based on this, it is estimated that perhaps 20% of sunlike stars have at least one giant planet while at least 40% may have planets of lower mass. [68] [69] [70] A 2012 study of gravitational microlensing data collected between 2002 and 2007 concludes the proportion of stars with planets is much higher and estimates an average of 1.6 planets orbiting between 0.5–10 AU per star in the Milky Way Galaxy, the authors of this study conclude "that stars are orbited by planets as a rule, rather than the exception." [3] Whatever the proportion of stars with planets, the total number of exoplanets must be very large. Since our own Milky Way Galaxy has at least 200 billion stars, it must also contain tens or hundreds of billions of planets. en.wikipedia.org [ This is a work in progress ] *...the proportion of stars with planets is ...1.6 planets orbiting between 0.5–10 AU per star in the Milky Way Galaxy...* What are the odds of us having 8 planets and a killer asteroid belt within one solar system? Do the numbers. youtube.com

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