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Wednesday, February 22, 2012

New Class of Extrasolar Planet Has Found

A new class of planets have been discovered by scientists from the NASA / ESA Hubble Space Telescope using. This planet is a water world that is enshrouded in a thick steamy atmosphere. A planet smaller than Uranus but larger than Earth. The study was led by Zachory Berta from the Harvard-Smithsonian Center for Astrophysics (CFA) was observed planet GJ 1214b. "GJ 1214b is like no planet we know of," Berta said. "A huge fraction of its mass is made up of water."

An artist view of GJ1214b is a super-Earth orbiting a red dwarf star 40 light-years from Earth. A waterworld enshrouded by a thick, steamy atmosphere. GJ 1214b represents a new type of planet, like nothing seen in the Solar System or any other planetary system currently known. Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics)

However, this planet actually had discovered by David Charbonneau in a MEarth Project of the CFA in 2009. This super-Earth is about 2.7 times Earth's diameter and weighing nearly seven-fold. It orbits a red dwarf star every 38 hours at a distance of 2 million miles, giving an estimated temperature of 230 degrees Celsius. Whereas in 2010, scientists from the CFA Jacob Bean and colleagues report that they have measured the atmosphere of GJ 1214b, discovered the possibility that planet consists of water. However, their observations can also be explained by the existence of planet-enshrouding fog in the atmosphere of GJ 1214b.

Berta and his co-authors, who include Derek Homeier of ENS Lyon, France, used Hubble's Wide Field Camera 3 (WFC3) to study GJ 1214b when it crossed in front of its host star. During such a transit, the star's light is filtered through the planet's atmosphere, giving clues to the mix of gases.

"We're using Hubble to measure the infrared colour of sunset on this world," Berta explained.

Hazes are more transparent to infrared light than to visible light, so the Hubble observations help to tell the difference between a steamy and a hazy atmosphere. They found the spectrum of GJ 1214b to be featureless over a wide range of wavelengths, or colours. The atmospheric model most consistent with the Hubble data is a dense atmosphere of water vapour. "The Hubble measurements really tip the balance in favour of a steamy atmosphere," Berta said.

From the observation found that the density is only about two grams per cubic centimetre. Water has a density of 1 gram per cubic centimetre, while Earth's average density is 5.5 grams per cubic centimetre. This suggests that GJ 1214b has much more water than Earth does, and much less rock.

As a result, the internal structure of GJ 1214b would be extraordinarily different from that of our world. "The high temperatures and high pressures would form exotic materials like 'hot ice' or 'superfluid water', substances that are completely alien to our everyday experience," Berta said.

Theorists expect that GJ 1214b formed further out from its star, where water ice was plentiful, and migrated inward early in the system’s history. In the process, it would have passed through the star’s habitable zone, where surface temperatures would be similar to Earth’s. How long it lingered there is unknown.

GJ 1214b is located in the constellation of Ophiuchus (The Serpent Bearer), and just 40 light-years from Earth. Therefore, it's a prime candidate for study by the NASA/ESA/CSA James Webb Space Telescope, planned for launch later this decade.

This article has edited by author of threelas
Source: http://www.spacetelescope.org/news/heic1204/

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