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Hot new planet could be in habitable zone -- barely

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Published : Sept. 13, 2011 - 10:32

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WASHINGTON (AP) -- Astronomers believe they have found a second planet outside our solar system that seems to be in the right zone for life, just barely.

But it would feel like a steam bath -- hot, sticky and beyond uncomfortable.

This undated handout image provided by The Europeans Southern Observatory shows a close-up of the sky around the star HD 85512. The picture was created from photographs taken through red and blue filters and forming part of the Digitized Sky Survey 2. The colored halos around the star, and the spikes of light, are artifacts of the telescope and are not real. The remarkable rocky planet HD 85512b that orbits this star is far too faint and too close in to be visible in this image.Astronomers have confirmed a second planet outside our solar system that seems to be in the right place for life -- just barely. But it would be a steam bath world: hot, sticky and downright uncomfortable. (AP-Yonhap News) This undated handout image provided by The Europeans Southern Observatory shows a close-up of the sky around the star HD 85512. The picture was created from photographs taken through red and blue filters and forming part of the Digitized Sky Survey 2. The colored halos around the star, and the spikes of light, are artifacts of the telescope and are not real. The remarkable rocky planet HD 85512b that orbits this star is far too faint and too close in to be visible in this image.Astronomers have confirmed a second planet outside our solar system that seems to be in the right place for life -- just barely. But it would be a steam bath world: hot, sticky and downright uncomfortable. (AP-Yonhap News)


European astronomers announced the discovery Monday along with about 50 other planets outside our solar system at a U.S. conference. The most exciting of those planets is only the second to be confirmed as lying in what astronomers call the habitable zone, or the Goldilocks zone. That means it is not too hot and not too cold for liquid water to be present. Water is the key to a planet being able to support Earth-like life, scientists say.

Only one of the past discoveries of such Goldilocks planets has held up. That was a planet found in 2007. And even this new one comes with an asterisk: The planet would need to have water and be a rocky, solid planet like Earth, not one that's primarily gas like Jupiter.

The new planet is about 3.6 times the mass of Earth. Temperatures there may range from 85 to 120 degrees (30 to 50 Celsius) with plenty of humidity.

``It's going to be really muggy, just think about the muggiest (Washington) day you can think of,'' said study author Lisa Kaltenegger, an astronomer with the Max Planck Institute in Germany. ``We're not saying it's habitable for you and me.''

But other types of life _ probably shorter and squatter life _ could conceivably take root there, she said. They would probably be closer to the ground than humans because gravity on this larger-than-Earth planet is about 1.4 times what we experience, she said.

For it to be considered livable by astronomers, at least 60 percent of it would have to be covered in clouds, said Kaltenegger. Earth has about 50 percent cloud cover, so 60 percent seems reasonable, she said.

The new planet, called HD85512b, closely circles a star about 35 light-years from Earth in the constellation Vela. Each light-year is 5.8 trillion miles. A year there is only 60 days. The only reason it might not too hot for life is that its sun is about 1,800 degrees (1,000 Celsius)cooler than our sun, Kaltenegger said.

The new batch of planets, including the potentially habitable one, were found by the European Southern Observatory's special planet-hunting instrument called HARPS is based in Chile. The finding doubles the number of planets that are closer to Earth in mass than those closer to Jupiter's size.

Reports on them appear in four papers published in scientific journals to coincide with the U.S. conference, Extreme Solar Systems II. This new planet was observed more than a thousand times over 200 nights of tracking from Chile so astronomers are confident with their findings, said study author Francesco Pepe of the Geneva Observatory in Switzerland.

In addition to the two European discoveries of potentially habitable planets, a NASA telescope has identified more than 50 other candidates, but those still need further confirmation.

 

<한글요약> 

생명체 존재 가능성 있는 '슈퍼지구' 발견



천문학자들이 새롭게 찾아낸 50개의 태양계 외 행성들 가운데 생명체 생존에 필수적인 물이 존재할 가능성이 있는 '슈퍼지구'가 발견됐다.

천문학자들은 HD85512b라는 이름의 이 행성이 태양과는 36광 년 떨어져 있으며, 태양보다 약간 작고 기온이 낮은 주황색 항성 HD85512의 주위를 59일 주기로 돌고 있다고 전했다.

'슈퍼지구'는 질량이 지구보다 훨씬 큰 지구형 행성을 뜻한다. 이번에 발견된 슈퍼지구는 행성 HD85512b는 지구보다 질량이 3.5배 더 크며 두번째로 발견된 슈퍼지구이다. 최초의 슈퍼지구 행성은 20 07년 칠레에서 발견된 '글리제 581d'다. 

행성 HD85512b는 항성 HD85512에서 기온이  가장 높은 가장자리 쪽에서 도는데, 이 부분의 대기 상태가 적절하다면 물이 존재할 가능성이 있다.

독일 하이델베르크 소재 막스 플랑크 천문학 연구소의 리자 칼텐네거는 이 행성 이 생명체가 살 수 있는 항성의 가장 따뜻한 가장자리에 있어 "마치 모닥불 바로 옆 에 있는 것과 같다"면서 "운이 좋다면 이 행성은 지구처럼 생명체가 살 수 있는  곳일 가능성이 있다"고 말했다.

칼텐네거는 이것이 행성 표면의 물이 끓지 못하도록 기온을 낮게 유지하기 위해 별빛을 반사할 수 있는 많은 구름층이 있어야 한다는 것을 의미한다고 설명했다.

천문학자들은 그러나 이 새로운 슈퍼지구에 대기가 존재하는지는 커녕 지구처럼 바위투성이인지 아니면 목성처럼 가스가 차있는지조차도 아직 알아내지 못했다.

또 이 행성의 대기 존재 여부를 확인하려면 천문학자들이 행성의 이미지를 촬영 해 물이나 이산화탄소, 기타 가스들의 흔적이 있는 밝은 부분을 분석해야 하지만, 현재로서는 이 같은 작업을 할 만큼 충분히 정밀한 망원경이 없는 상황이다.

이에 대해 유럽남부천문대의 마르쿠스 키슬러-파티그는 내년에 완공될 유럽초극 대망원경이 이 작업을 해낼 것으로  기대했다.