CCTV.com - CNTV English - CCTV News

Astronomers reveal new type of planet

02-22-2012 10:00 BJT

WASHINGTON, Feb. 21 (Xinhua) -- Using Hubble space telescope, an international team of astronomers have come up with a new class of planet, according to a report published online Tuesday in The Astrophysical Journal.

By analyzing the previously discovered world GJ1214b, the team led by Harvard-Smithsonian Center for Astrophysics (CfA) astronomer Zachory Berta proved that it is a water world enshrouded by a thick, steamy atmosphere.

Our solar system contains three types of planets: rocky, terrestrial worlds (Mercury, Venus, Earth, and Mars), gas giants ( Jupiter and Saturn), and ice giants (Uranus and Neptune). Planets orbiting distant stars come in an even wider variety, including lava worlds and "hot Jupiters".

"GJ1214b is like no planet we know of," said Berta in a statement issued Tuesday. "A huge fraction of its mass is made up of water."

GJ1214b was discovered in 2009 by the ground-based MEarth Project. This super-Earth is about 2.7 times Earth's diameter and weighs almost seven times as much. It orbits a red-dwarf star every 38 hours at a distance of 1.3 million miles, giving it an estimated temperature of 230 degree Celsius.

In 2010, CfA scientist Jacob Bean and colleagues reported that they had measured the atmosphere of GJ1214b, finding it likely that the atmosphere was composed mainly of water. However, their observations could also be explained by the presence of a world- wide haze in GJ1214b's atmosphere.

Berta and his co-authors used Hubble's WFC3 instrument to study GJ1214b 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. Hazes are more transparent to infrared light than to visible light, so the Hubble observations help tell the difference between a steamy and a hazy atmosphere.

They found the spectrum of GJ1214b to be featureless over a wide range of wave lengths, or colors. The atmospheric model most consistent with the Hubble data is a dense atmosphere of water vapor.

"The Hubble measurements really tip the balance in favor of a steamy atmosphere," said Berta.

Since the planet's mass and size are known, astronomers can calculate the density, which works out to about two grams per cubic centimeter. Water has a density of one gram per cubic centimeter, while Earth's average density is 5.5 gram per cubic centimeter. This suggests that GJ1214b has much more water than Earth, and much less rock. As a result, the internal structure of GJ1214b would be very different than our world.

Theorists expect that GJ1214b formed farther 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.

GJ1214b is located in the direction of the constellation Ophiuchus, and just 40 light years from Earth. It's a prime candidate for study by the next-generation James Webb Space Telescope.

Editor:Wang Lingfei |Source: Xinhua

Hot Videos view more

The celebrations are still continuing as the victorious coach, Joachim Loew, has been honored for his achievement in his hometown of Freiburg.
Germany coach Loew honored in hometown of Freiburg

Chinese men´s national team continued its preparations for next year´s Asian Cup, as they managed a one-all draw against visitors Jordan during a football friendly in Harbin, the capital city of Northeast China´s Heilongjiang Province.
China held to 1-1 draw by Jordan

The defending world champs came into the contest with a perfect 6-and-oh record, but they would be in for a tough first half before opening things up in the second.
USA beat Slovenia 119-76 in quarter-finals

Hot Stories more

UK authorities believe killer of James Foley is a British national

Across the UK the hunt is on for James Foley’s killer, who authorities believe is a British national. As Richard Bestic reports from London, Prime Minister David Cameron cut short his summer break to lead his government’s response.

Israeli war jets renews Gaza strike as truce talks stalled

Three Palestinians were killed and 40 others wounded in the intensive Israeli war jets´ airstrikes on the Gaza city on Tuesday night, shortly before an end of a 24-hour ceasefire in the Gaza Strip,

Missouri police arrest dozens after violent night

As the protests in the town of Ferguson, Missouri turned violent with police facing ´heavy gunfire´ from some ´criminal elements´, cops fired tear gas, stun grenades and arrested 31 demonstrators on Monday night.

Picture in news more

More Video News

Choose TV Program