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 2,500 F (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."

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.