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Scientists detect hottest exoplanet yet

It's dense, gassy and a bit of oddball, but a planet orbiting a star in the constellation Hercules may be the hottest known yet, scientists say. Meanwhile, other researchers say they've created the first-ever climate map of a world beyond our solar system.
This artist's conception shows what may be the hottest-known planet beyond our solar system, with temperatures rising to 3,700 degrees Fahrenheit. A red "evil eye" is thought to stare directly at its host star.
This artist's conception shows what may be the hottest-known planet beyond our solar system, with temperatures rising to 3,700 degrees Fahrenheit. A red "evil eye" is thought to stare directly at its host star.Spitzer Space Telescope / T. Pyle / SSC / JPL-Caltech / NASA
/ Source: Reuters

It's dense, gassy and a bit of oddball, but a planet orbiting a star in the constellation Hercules may be the hottest known yet, scientists say.

The planet — HD 149026b — is smaller than the typical gas giant, and its atmosphere is much heavier, contributing to its staggering temperature of 3,700 degrees Fahrenheit (2,040 degrees Celsius), they said.

The discovery came to light as a separate group of astronomers announced the first-ever climate map of a more typical gas giant.

Both findings, reported in Thursday's issue of the journal Nature, will help scientists gain a better understanding of climate on planets outside our solar system.

The evil-eye planet
The University of Central Florida's Joseph Harrington described the hot planet as a black ball with a red spot staring right at its star. "It looks like the evil eye," he said in a telephone interview.

The planet is a so-called "hot Jupiter," a gas giant that orbits very close to its star.

It is one of 14 planets detected beyond our solar system that is known to pass in front of and behind its parent star as seen from Earth. Such worlds are known as transiting planets.

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By measuring changes in the amount of light given off by the star as the planet crosses its path, Harrington and colleagues were able to to deduce its temperature.

"This planet is off the temperature scale that we expect for planets," said Drake Deming of NASA's Goddard Space Flight Center, who worked on the study.

Harrington said for a planet to get so hot, it must be absorbing most of the light that reaches it. That light is radiated back in the form of a dim red glow.

HD 149026b is located 279 light-years from Earth, with a light-year being the distance light travels in a year — about 6 trillion miles (10 trillion kilometers).

Mapping a faraway gas giant
While Harrington and colleagues have found the most extreme of the hot Jupiters, researchers at the Harvard-Smithsonian Center for Astrophysics have created a rough climate map for a more garden-variety gas giant.

Spitzer Space Telescope / Spitzer Space Telescope

Using NASA's Spitzer space telescope, researchers measured changes in infrared light coming from the planet HD 189733b in the constellation Vulpecula, 60 light-years from Earth. The planet is tidally locked to its star, so that one side always faces the star and the other side is always dark.

What the study revealed is a planet with supersonic winds more than six times faster than those on Jupiter that are distributing heat evenly around the planet, even the side that does not face its sun.

"You've got this big belt of wind that is whipping around the planet," Heather Knutson of the Harvard-Smithsonian Center said in a telephone interview.

Harrington said Knutson's work will come to serve as the model for mapping climate on other planets.

"It's a Rosetta Stone," he said.