August 24, 2011
Astronomers Find Potential Super-Earth
A team of scientists at Germany´s Max-Planck Institute for Astronomy has discovered a potentially habitable planet about 3.6 times as massive of Earth orbiting the star HD 85512, roughly 36.23 light years away (one light year is equivalent to roughly 5.9 trillion miles).
Dan Vergano of USA Today reports that the discovery, led by the institute´s Lisa Kaltenegger, adds to the 572 planets orbiting nearby stars listed by the Extrasolar Planets Catalogue. Astronomers around the world have been vying to claim the first Earth-like inhabitable planet orbiting a star in our Sun´s own neighborhood.
The planet is judged by the inner edge of HD 85512´s habitable zone. “The inner edge of the (Habitable zone) denotes the location where the entire water reservoir can be vaporized by runaway greenhouse conditions, followed by the photo-dissociation of water vapor and subsequent escape of free hydrogen into space,” said the institute´s Lisa Kaltenegger, who led the team in the discovery of the planet.
“The outer boundary denotes the distance from the star where the maximum greenhouse effect fails to keep CO2 from condensing permanently, leading to runaway glaciation,” she added.
In a companion study led by Francesco Pepe of the Swiss Observatoire de Geneve, a European planet-hunting team reported that HD85512 is the one star among 10 nearby ones surveyed with a planet in the “habitable zone,” where water remains liquid, rather than freezing of boiling and vaporizing. The planet orbits its star once every 54 days on a slightly elongated orbit with a 24 million mile radius, the study reports.
Pepe´s study is also released on the arXiv database, an archive of preprints in the scientific community. The reports can be found at http://arxiv.org/ftp/arxiv/papers/1108/1108.3561.pdf and http://arxiv.org/PS_cache/arxiv/pdf/1108/1108.3447v1.pdf.
An atmospheric model calculating the greenhouse effect of an atmosphere on the planet finds that it would most likely be a pretty cloudy place, about half covered in clouds (a 0.5 albedo or reflectivity value) to reflect enough starlight away from the planet to keep it potentially habitable. Pepe´s study states that Earth has a 0.3 albedo and Venus a 0.75 albedo. Surface gravity on the new planet would be about 1.4 times stronger than on Earth.
Many European astronomers, most notably Pepe, have criticized a University of California research team´s report of a possible habitable planet orbiting another star, Gliese 581, while noting their own separate candidate circling the same star.
Pepe´s study was part of the High Accuracy Radial velocity Planet Searcher (HARPS), a high-precision echelle spectrograph installed in ESO´s 3.6m telescope at La Silla Observatory in Chile in 2002. HARPS is one of only two instruments in the world capable of finding planets with extreme accuracy.
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