WASHINGTON (AFP) ― NASA has spotted a tiny, rocky planet about the size of Earth doing a speedy orbit of a star outside our solar system, but its scorching temperatures are too hot for life, the space agency said Monday.
The exoplanet, named Kepler-10b, is the smallest-ever planet discovered outside our solar system, and was located by NASA’s Kepler spacecraft.
It is about 1.4 times the size of Earth and spins around its star more than once a day, an orbit much too close for life to survive.
“Kepler-10b is definitely NOT in the habitable zone as we define it. The dayside temperature of the planet is expected to be higher than 1,371 Celsius!!” NASA expert Natalie Batalha said in a web chat to describe the discovery.
“That’s hot enough to melt iron!” she added.
“It wouldn’t be a very nice place for organisms like those on Earth to live. Carbon-based chemistry wouldn’t thrive there. Molecules comprising RNA and DNA couldn’t stay intact in such extreme temperatures.”
This NASA artist’s concept shows the smallest star known to host a planet. (AFP-Yonhap News)
The planet completes a full orbit once every 0.84 days, and is 23 times closer to its star than Mercury is to our sun.
According to Douglas Hudgins, Kepler program scientist at NASA, the discovery is promising even though no life could exist there.
“The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own,” said Hudgins.
“Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come,” he said.
The new planet has a mass 4.6 times that of the Earth, and an average density of 8.8 grams per cubic centimeter, similar to an iron dumbbell, NASA said.
The findings are described in the Astrophysical Journal.
Batalha, a professor at San Jose State University and deputy science team lead for NASA’s Kepler Mission, said that there is evidence of another potential planet in the same star system, but little is yet known about it.
“There is actually already a very compelling signature of another potential planet in this system,” said Batalha.
“There is a transit event that recurs once every 45 days and is suggestive of a planet a bit larger than two times the radius of the Earth.”
Kepler is NASA’s first mission in search of Earth-like planets orbiting suns similar to ours.
It launched in 2009, equipped with the largest camera ever sent into space
― a 95-megapixel array of charge-coupled devices ― and is expected to continue sending information back to Earth until at least November 2012.
The space telescope is searching for planets as small as Earth, including those orbiting stars in a warm, habitable zone where liquid water could exist on the surface of the planet.
NASA defines the habitable zone, in part, to have a temperature below the boiling point of water and higher than the freezing point.
Kepler is not equipped to detect signs of life, such as the presence of oxygen in the atmosphere, but mainly aims to locate Earth-size planets outside our solar system.
<한글 요약> <관련 기사>
나사, 태양계밖 가장 작은 행성 발견
나사(미국 항공우주국)는 10일 태양계 밖에서는 가장 작은 행성을 발견했으며 이 행성은 지구처럼 암석이 있는 행성이라고 밝혔다.
이 행성 한 면의 온도는 섭씨 1500도에 달하며, 생물이 살기에는 너무 뜨겁다고 한다. 이 행성의 이름은 행성을 발견한 망원경의 이름을 따서 '케플러(Kepler) 10-b'로 붙여졌다.
나사의 과학자 나탈리 바탈라는 케플러 10-b가 지구 크기의 1.4배이며 지구 질량의 4.5배라고 말했다.
앞서 천체학자들은 태양계 밖에서 지구와 질량이 비슷한 다른 행성들을 찾아냈지만, 이처럼 작은 행성은 발견하지 못했다.
케플러 10-b의 온도가 높은 이유는 이 행성과 자신의 항성간 거리가 수성과 태양간 거리의 20분의 1에 불과하기 때문이라고 한다.