NASA has spotted a tiny, rocky planet about the size of Earth doing a speedy orbit of a star outside our solar system, the space agency has announced.
The exoplanet, named Kepler-10b, is the smallest-ever planet discovered outside our solar system, but its scorching temperatures are too hot for life.
The planet, which was located by NASA's Kepler spacecraft findings, is described in a paper to be published in The Astrophysical Journal.
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 2500°F (1371°C)", says NASA expert Natalie Batalha. "That's hot enough to melt iron."
"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."
The planet completes a full orbit once every 0.84 days, and is 23 times closer to its star than Mercury is to the Sun.
Finding a 'significant milesone'
According to Dr 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," says 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 centimetre, similar to an iron dumbbell, says NASA.
Batalha, a professor at San Jose State University and deputy science team lead for NASA's Kepler Mission, says 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," says 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