Earth-like Planets are Common in Universe!!
October 29, 2010
Planet Earth is not so special after all; there’s one orbiting roughly every one in four Sun-like stars, according to a five-year astronomy study. The study, published in the journal Science, used Hawaii’s twin 10-metre Keck telescopes to scan 166 sun-like stars within 80 light years, or about 757 trillion kilometres. The team spotted 22 planets around 33 of these stars by the gravitational tug of the planets – called the Doppler or radial velocity method.
23 Earths for every 100 Suns
Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune,and about 12 have super-Earths between three and 10 Earth masses. How tough the search for habitable worlds would be wasn’t at all clear when NASA gave the Kepler team the go-ahead almost 10 years ago. Only huge, scorching-hot exoplanets larger than Jupiter had been found by then. Limitations in the technique mean astronomers can’t yet see planets up to three times Jupiter’s mass orbiting within one quarter of the distance of the Earth to the Sun (1 AU or almost 150 million kilometres), or smaller Earth-like planets much close in.
Image: The data, depicted here in this illustrated bar chart, show a clear trend. Small planets outnumber larger ones. Astronomers extrapolated from these data to estimate the frequency of the Earth-size planets — nearly one in four sun-like stars, or 23 percent, are thought to host Earth-size planets orbiting close in. Each bar on this chart represents a different group of planets, divided according to their masses. In each of the three highest-mass groups, with masses comparable to Saturn and Jupiter, the frequency of planets around sun-like stars was found to be 1.6 percent. For intermediate-mass planets, with 10 to 30 times the mass of Earth, or roughly the size of Neptune and Uranus, the frequency is 6.5 percent. And the super-Earths, weighing in at only three to 10 times the mass of Earth, had a frequency of 11.8 percent. NASA/JPL-Caltech/UC Berkeley[via: Centauri Dreams]
One of astronomy’s goals is to find eta-Earth (η-Earth), the fraction of Sun-like stars that have an Earth. This is a first estimate, and the real number could be one in eight instead of one in four. But it’s not one in 100, which is glorious news. What this means is that, as NASA develops new techniques over the next decade to find truly Earth-size planets, it won’t have to look too far. Greenhill’s expertise is in the ‘microlensing technique’, which looks at the bending of light of a source star by an intervening planet-star system and is particularly suitable for finding small-mass planets. He estimates between 32% and 100% of stars have planets two to 10 times the size of Earth in orbits ranging from 1¬-10 AU. That’s one heck of a lot of Earth-mass planets. I don’t care how small the probability of life is; some of them are bound to have water on them and will probably have life there.
Remark: It simply suggests that there could be more and more Earth like planet irrespective to our probablistic estimations. In a previous article , I’ve presented a detailed information about temporal temperature zones and wind maps, which supports my earlier speculation of planet being habitable . In that article you can see that wind flow maps of Gliese 581g are similar to wind map of planet Earth at various locations. All of these calculations and evidences dismay the idea of planet being inhabitable. Now this study presents even more optimistic speculation as to how common Earth like planets are. Rare Earth hypothesis goes to hell.
[Source: Cosmos Magazine]
[Note: In original article they referred 80million light years as ~757 trillion kilometers. There should be instead 80 light years.]