Astronomers say a newly discovered planet almost next door to us — just 39 light-years away — is the closest rocky exoplanet like Earth ever found.

It's not like Earth in one respect, though: the atmosphere in its coolest parts is a sizzling 450 to 500 degrees Fahrenheit, making it more like our solar system neighbor Venus than our own world, scientists say.

Still, the planet's proximity to us and its resemblance to Earth in at least its diameter and mass make it "arguably the most important planet ever found outside the solar system," Drake Demming of the University of Maryland wrote in a commentary accompanying the published study on the discovery.

Just 16 percent larger than Earth, the planet GJ 1132b orbits a dim star just one-fifth the size of our sun.

It's close to its parent star, orbiting at just 1.4 million miles away. For comparison, Mercury in our solar system orbits our sun at 36 million miles.

At just 39 light-years away, its parent star, Gliese 1132, is a close neighbor in the Milky Way.

"Our galaxy spans about 100,000 light-years," said Zachory Berta-Thompson, a postdoctoral researcher at MIT's Kavli Institute for Astrophysics and Space Research. "So this is definitely a very nearby solar neighborhood star."

The planet GJ 1132b is probably tidally locked in its orbit, which means it always presents the same face to its star, creating a permanent and unchanging day and night side.

Because of its sizzling temperature, it's unlikely to retain liquid water on its surface, making it almost certainly uninhabitable, the scientists say.

Still, it's cool enough to have retained a significant atmosphere, they point out, which makes it an interesting subject for study.

"If we find this pretty hot planet has managed to hang onto its atmosphere over the billions of years it's been around, that bodes well for the long-term goal of studying cooler planets that could have life," explained Berta-Thompson.

Its nearness provides an unprecedented opportunity to make observations, since most Earth-sized planets discovered so far are thousands of light-years distant from us.

"We finally have a target to point our telescopes at, and [can] dig much deeper into the workings of a rocky exoplanet, and what makes it tick," Berta-Thompson said.

While it may be more like Venus than the Earth, it will allow scientists to test theories about rocky planets, how they form, how they end up in their particular orbits and what physical process takes place on their surfaces.

Meanwhile, nobody's complaining.

"Our ultimate goal is to find a twin Earth, but along the way we've found a twin Venus," said astronomer David Charbonneau of the Harvard-Smithsonian Center for Astrophysics. "We suspect it will have a Venus-like atmosphere too, and if it does we can't wait to get a whiff."

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