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Kepler detects five 'hot Jupiters' in six weeks

Posted: January 4, 2010

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A robotic planet-hunting telescope in deep space has detected five new blistering worlds beyond the solar system, but the Kepler probe's search for Earth-like planets is just beginning.

An artist's concept of a Jupiter-like planet orbiting close to its parent star. Credit: NASA/JPL-Caltech/T. Pyle (SSC)
The new planets are unlike any body in our solar system. All five worlds are gas giants orbiting incredibly close to their parent stars and are hotter than molten lava, according to William Borucki, the Kepler mission principal investigator at NASA's Ames Research Center.

Two of the planets have temperatures of about 3,000 degrees Fahrenheit, hot enough to melt iron. The planets are called "hot Jupiters" because of their high mass and blazing temperatures.

"They all simply glow with their temperatures," Borucki said.

Life as we know it could not survive on such worlds, according to astronomers.

"Looking at them might be like looking at a blast furnace," Borucki said. "Certainly no place to look for life. That will be coming later."

The planets are bombarded with heat because of their perilous proximity to ther parent stars. The bodies complete a circuit around their stars between 3.2 and 4.9 Earth days, according to scientists.

Four of the worlds are larger or more massive than Jupiter. Another planet is comparable to Neptune. The planets are named Kepler 4b, 5b, 6b, 7b and 8b.

The planets join more than 400 other worlds scientists have detected around other stars through ground and space telescopes.

Scientists announced the discovery Monday at an American Astronomical Society meeting in Washington. The planets are the first to be discovered by the Kepler telescope, a $591 million mission to seek out small Earth-like planets that could harbor life.

The planets were observed in the first 43 days of Kepler's science mission. Astronomers are now sifting through eight more months of data to search for more exoplanets.

"These are very short orbits because we used just the first few weeks of data to quickly find these candidates and go to a ground-based program, which required several months before we could confirm any planet," Borucki said.

Kepler searches for exoplanets by watching for dips in a star's light, indicating a planet could be passing between the spacecraft and the star.

The spacecraft's 3.1-foot telescope is staring at more than 150,000 stars in a patch of the sky in the Cygnus and Lyra constellations, continuously measuring starlight with a 95-megapixel photometer, or camera.

An artist's concept of Kepler. Credit: NASA
The probe launched in March 2009 and started collecting science data two months later. Kepler will operate through at least November 2012.

Kepler must observe at least three transits of a potential planet, and astronomers analyze follow-up data before confirming an exoplanet's existence.

The exhaustive process ensures instrument issues or other natural phenomena are not responsible for the variations in observed light.

So far, scientists have only been able to make the case for the five planets revealed Monday.

"Beautiful match," Borucki said. "This completely confirms that we really have planets here."

Researchers verified the first five exoplanets relatively quickly because of their short orbital periods. Smaller planets with longer orbits and cooler temperatures will take years to confirm because they less frequently pass in front of their stars.

"We will find many planets with longer period orbits and planets that are cooler than what we have seen," Borucki said.

It may take three years to find rocky, Earth-like, potentially habitable exoplanets around stable stars similar to the sun, said Jon Morse, director of NASA's astrophysics division.

"We expected Jupiter-size planets in short orbits to be the first planets Kepler could detect," Morse said. "It's only a matter of time before more Kepler observations lead to smaller planets with longer period orbits, coming closer and closer to the discovery of the first Earth analog."

Scientists consider exoplanets habitable if they are at the right temperature to support liquid water. For stars like the sun, the habitable zone extends between where Venus and Earth reside.

"We'll find a diversity of structure and material, and we'll explore new worlds that only Kepler can allow us to reach," said Dimitar Sasselov, a Kepler science team member from the Harvard-Smithsonian Center for Astrophysics.

The science team is currently evaluating a "tidal wave" of data and analyzing hundreds of exoplanet candidates. NASA could announce more discoveries in the coming months.

"We're beginning to understand what fraction of planets are icy, what fraction of planets are steam planets, and what fraction of planets are Jupiter-like," said Catherine Pilachowski, an astronomer at Indiana University.