Researchers find “super-earth” in habitable zone
The potentially habitable "super-earth" in a nearby star system around a dwarf sun at just the right distance for moderate temperatures at which water would be liquid, as the researchers write in the astrophysical journal letters. Flowing water is considered a basic prerequisite for life as we know it. However, researchers have not yet found any evidence of the existence of water or even life on the so-called exoplanet.
But lead author guillem anglada-escude of the carnegie-institution in washington is sure: "this planet is the new best candidate for conditions, which permit liquid water and perhaps life, as we know it", judges the researcher, who works in the meantime at the university of gottingen, in a communication. The now discovered planet has at least 4.5 times as much mass as our earth and orbits its home star in only 28 days. It is thus much closer to its star than the earth is to the sun. Nevertheless, according to astronomers’ calculations, it should be as warm on the super-earth as it is on our home planet. For its sun is a so-called dwarf star of the M-class, which radiates much more weakly than our sun. Overall, the newly discovered super-earth receives about ten percent less light than the earth receives from the sun, astronomers report.
"Super-earth" – this is not a quality judgement. But astronomers use this term to describe exoplanets that are coarser, but not very much coarser, than the earth, and probably made of rock like it. This is in contrast to the jupiterahnlichen planets, which are gigantic gas balls like the coarse planet of our system. The now discovered extrasolar planet (exoplanet) is not the first super-earth that astronomers have tracked down. Also in the habitable zone of other stars researchers have repeatedly tracked down exoplanets.
In total, more than 750 planets have been found in other stars using various methods. Recent calculations even suggest that there are more planets in the milky way than stars. However, there are no signs of life from any of them so far.
The home star of the now discovered super-earth has the catalog number GJ 667C and is 22 light-years away from our solar system. It belongs therefore to our cosmic neighborhood. According to the researchers’ analysis, it has at least one other planet orbiting the star in only 7.2 days. Possibly it possesses even still another super earth as well as a coarse gas planet, which orbit it in coarser distance.
The researchers stumbled on the planets by a regular back and forth tumbling of the dwarf star, which arises when the gravity of its companions tugs at it. The tumbling star moves sometimes away from the earth and then again toward it. As a result, its light sometimes appears a little redder and then bluer again – just as the siren of an approaching fire engine sounds brighter and brighter, while that of a receding fire engine sounds darker and darker. This doppler effect is how most of the exoplanets discovered so far have given themselves away.
The discovery at GJ 667C surprised the astronomers, however. Because the dwarf sun belongs to a triple star system which, compared to our sun, has only a few heavier chemical elements such as iron, carbon and silicon, of which rocky planets such as the earth are composed. "This star was considered a pretty unlikely home for planets," co-author steven vogt of the university of california in santa cruz explained in a news release from his university. M-class dwarfs such as GJ 667C are among the most common stars in the milky way. "The discovery of this planet, so close and so early, suggests that our galaxy is teeming with billions of potentially habitable rocky planets."
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