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 Batch of Fifty New Alien Worlds Discovered

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Join date : 2010-07-22
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PostSubject: Batch of Fifty New Alien Worlds Discovered   Wed Sep 14, 2011 12:06 am

Batch of Fifty New Alien Worlds Discovered

Astronomers have announced the discovery of 50 (yes, five-zero) exoplanets, the largest group of alien worlds announced at one time.
Sixteen of these worlds are "super-Earths" -- exoplanets that possess masses larger than Earth, yet much lower than the gas giants.

This time, however, the announcement doesn't come from NASA's orbital exoplanet hunter, the Kepler Space Telescope, it comes from the European Southern Observatory's (ESO) High Accuracy Radial velocity Planet Searcher (or HARPS for short). As with any exoplanet announcement comes the question: are any of these newly discovered worlds suitable for life? And, in this case, the answer is: maybe.

Enter HD 85512b, an exoplanet with a mass 3.6 times that of the Earth. This "super-Earth" is exciting in that not only can it be
considered a jumbo-sized Earth, it also orbits its sun-like star (HD 85512) on the inner rim of the star's habitable zone.

"This is the lowest-mass confirmed planet discovered by the radial velocity method that potentially lies in the habitable zone of its star,
and the second low-mass planet discovered by HARPS inside the habitablezone," said Lisa Kaltenegger, of the Max Planck Institute for
Astronomy, Heidelberg, Germany and Harvard Smithsonian Center for Astrophysics, Boston, who is an expert on the habitability of
exoplanets. HARPS contrasts greatly from the methods employed by Kepler to detect exoplanets. Located at La Silla Observatory in Chile, HARPS is a spectrometer that analyzes the light from stars.

Over a period of time, HARPS may detect a slight shift in a target star's frequency. If this shift is periodic, it means something is
orbiting the star. By precisely measuring the tiny shift, the HARPS team can deduce the orbiting body's mass and orbital period (its orbital
radius can therefore be calculated). However, one thing HARPS cannot deduce is an exoplanet's physical size. Therefore, although finding a 3.6 Earth mass world is exciting, we haveno idea whether it's the same size of the Earth, or puffed up like a mini-Neptune. Therefore, we have no idea if HD 85512b is rocky, or gaseous, or something more exotic. This is where Kepler is different, it is able to deduce exoplanets' physical size. When a world passes in front of its parent star, the exoplanet's silhouette will block a certain amount of light, relating to its physical size. But Kepler can only see exoplanets if they are orbiting their star "edge-on" -- making HARPS's "radial velocity method" a very powerful tool for detecting worlds that would otherwise remain hidden from Kepler's "transit method" eye.

Also, HARPS is no newbie to the field of exoplanet hunting. In the last eight years the instrument has detected 150 new exoplanets, and
with the help of these new data, it has made a groundbreaking discovery: Approximately 40 percent of sun-like stars possess at least one exoplanet less massive than Saturn. Also, the majority of exoplanets of Neptune mass or less appear to be in systems with multiple planets.

Needless to say, this finding will reinvigorate the discussions of the potential for life on these low-mass worlds, particularly when
super-Earths are pottering around inside their stars' habitable zones But as discussed by Ray Villard, dry, desert worlds may have a higher likelihood of supporting alien life than worlds drenched in water, like Earth. Therefore, desert planets have habitable zones three-times wider than Earth-like worlds.

The scope for the existence of extraterrestrial life appears to have widened, too.

Image credit: ESO/M. Kornmesser

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