SOURCE: World Science
Jan. 25, 2006
Special to World Science
Astronomers say they have found the smallest planet ever detected around a normal star outside our solar system, and that the discovery suggests there are many Earth-like planets out there.
The planet weighs five times as much as Earth and orbits a relatively cool star, known as a red dwarf, every decade, astronomers said.
It would thus be the latest in a series of discoveries of increasingly Earth-like planets outside our solar system, since others found to date are even larger compared to Earth.
Also, with the finding, astronomers have now identified planets on both sides of the “habitable zones” of distant stars.
A habitable zone is a narrow region around a star whose temperature is such that liquid water can exist, so that presumably life can form.
Most planets found around stars other than the Sun, called extrasolar planets, to date have been in the hotter-than-habitable zone. The newfound world, by contrast, is too cold, astronomers said, suggesting the discovery of a planet lying in the lucky middle might not be far off.
“It’s encouraging that we now have examples of planets on both sides of the habitable zone,” said Scott Tremaine of Princeton University in Princeton, N.J., one of the astronomers who announced the finding.
The distance between the planet and its star is about three times that between the Earth and the Sun, the researchers found. That would put it somewhere between Mars and Jupiter in terms of distance from its host star.
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