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Sun, October 31, 2010
Galaxy may have gobs of Earth-size planets
By Marc Kaufman
Galaxy may have gobs of Earth-size planetsBy Marc Kaufman Washington Post Staff Writer
Friday, October 29, 2010 >
Nobody has seen them yet, but scientists now think there are tens of billions of planets the general size and bulk of Earth in the Milky Way galaxy alone - a startling conclusion based on four years of viewing a small section of the nighttime sky.
The estimate, made by astronomers Andrew Howard and Geoffrey Marcy of the University of California at Berkeley, flows from the logic that the number of small but detectable exoplanets - planets outside Earth's solar system - is substantially larger than the number of big exoplanets in distant solar systems.
In a paper released Thursday by the journal Science, the two report that based on this galactic preference for smaller planets, they think that almost one-quarter of the stars similar to our sun have Earth-size planets orbiting them.
"This is the first estimate based on actual measurements of the fraction of stars that have Earth-size planets," said Marcy, who did his observing with Howard at the Keck Observatory in Hawaii.
Their observations and extrapolations say nothing about whether these Earth-size planets will have the characteristics of Earth: its density, a distance from the sun that is just right for liquid water, the fact that it is a rocky structure rather than a gaseous ball.
But Marcy said that with so many Earth-size planets now expected to be orbiting distant suns - something on the order of 50,000,000,000,000,000,000,000 across the universe - the likelihood is high that many are in "habitable zones" where life can theoretically exist.
"It's tantalizing, without a doubt, to think some of those Earths are in habitable zones," Marcy said. "And based on what we know, really, why wouldn't they be?"
Planet-hunting technology allows astronomers to find exoplanets down to the size of super-Earths that are three times the size of our planet. The new conclusion that billions of planets similar in mass (or bulk) to Earth exist in the Milky Way is based on extrapolations of the number of these super-Earths compared with the number of larger exoplanets. Because the finding is not based on firm measurements, Marcy said, "it's a very exciting set of numbers that we have confidence in, but there are yellow flags."
Exoplanet hunters, who found the first planet outside our solar system in 1995, are entering a period of especially heightened and excited discovery. The new assessment from Howard and Marcy, funded by NASA and the Keck Observatory, comes only weeks after two other astronomers published a paper saying they had detected an apparently rocky planet in a habitable zone around a star relatively close to Earth called Gliese 581g.
That conclusion, by Steven Vogt of the University of California at Santa Cruz and Paul Butler of the Carnegie Institution in Washington, has not been confirmed, and some have challenged the discovery, especially a Swiss team that has been a leader in exoplanet research.
But the assessment that Earth-size planets are ubiquitous in distant solar systems is expected to get additional support in February when the scientists operating NASA's Kepler Mission, which is searching for Earth-size and habitable planets, report on what they have been finding.
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From The Urantia Book:
"The Grand Universe is the present organized and inhabited creation. It consists of the seven superuniverses, with an aggregate evolutionary potential of around seven trillion inhabited planets, not to mention the eternal spheres of the central creation. But this tentative estimate takes no account of architectural administrative spheres, neither does it include the outlying groups of unorganized universes. The present ragged edge of the grand universe, its uneven and unfinished periphery, together with the tremendously unsettled condition of the whole astronomical plot, suggests to our star students that even the seven superuniverses are, as yet, uncompleted. As we move from within, from the divine center outward in any one direction, we do, eventually, come to the outer limits of the organized and inhabited creation; we come to the outer limits of the grand universe. And it is near this outer border, in a far-off corner of such a magnificent creation, that your local universe has its eventful existence." 12:1.13
"The Satania system of inhabited worlds is far removed from Uversa and that great sun cluster which functions as the physical or astronomic center of the seventh superuniverse. From Jerusem, the headquarters of Satania, it is over two hundred thousand light-years to the physical center of the superuniverse of Orvonton, far, far away in the dense diameter of the Milky Way. Satania is on the periphery of the local universe, and Nebadon is now well out towards the edge of Orvonton. From the outermost system of inhabited worlds to the center of the superuniverse is a trifle less than two hundred and fifty thousand light-years." 32:2.11
"Your world is called Urantia, and it is number 606 in the planetary group, or system, of Satania. This system has at present 619 inhabited worlds, and more than two hundred additional planets are evolving favorably toward becoming inhabited worlds at some future time."15:14.5
"The myriads of planetary systems were all made to be eventually inhabited by many different types of intelligent creatures, beings who could know God, receive the divine affection, and love him in return. The universe of universes is the work of God and the dwelling place of his diverse creatures. 'God created the heavens and formed the earth; he established the universe and created this world not in vain; he formed it to be inhabited.' " 1:0.2
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