On this planet as dense as Iron, a year lasts only eight hours

There is no saying what the universe might throw at us. Just when some of us think they know everything about it, a new discovery tosses all that smugness out of the park. 

Scientists have now spotted one of the smallest planets ever to be discovered outside our solar system. The planet, designated as GJ 367b is a red-hot world. It's just a bit larger than Mars and is as dense as pure Iron. 

The planet zooms around its star every eight hours. It is 31 light-years away from Earth.

Scientists are eager to find exoplanets, as these alien worlds are known, that might harbor life. The newly discovered one, called GJ 367b, certainly could not, possessing ferocious surface temperatures and perhaps a molten lava surface on the side facing its star, they said. But other small exoplanets found and studied using the same methods might emerge as good candidates for nurturing extraterrestrial life.

A quarter century after the first exoplanet discoveries, scientists have turned toward characterizing them more precisely to gain a deeper understanding of their variety, from large gas giants akin to Jupiter to smaller rocky Earth-like planets where life might thrive.

"Gas giants such as Jupiter, as we know it, are not habitable because they have more extreme temperatures, weather, pressures and a lack of essential building blocks to support life," said astronomer Kristine Lam of the Institute of Planetary Research at the German Aerospace Center (DLR), lead author of the study published in the journal Science. She was quoted by Reuters.

"Unlike gas giants, small terrestrial worlds like Earth are more temperate and consist of important ingredients, such as liquid water and oxygen, to harbor life forms. Although not all terrestrial exoplanets are habitable, searching for smaller worlds and identifying the type of planets they are can help us understand how planets were formed, what makes a planet habitable and if our solar system is unique," Lam added.

GJ 367b is the smallest exoplanet to be so precisely characterized. It has a diameter of about 5,600 miles (9,000 km) - compared to Earth's 7,900 miles (12,700 km) and the 4,200 miles (6,800 km) of Mars. Its mass is 55% that of Earth and it is more dense - near that of pure iron.

The researchers calculated that 86% of GJ 367b is composed of iron, with an interior structure resembling Mercury, the closest planet to our sun. They are wondering whether the planet lost an outer mantle that once encased its core.

"Perhaps like Mercury, GJ 367b could have experienced an episode of giant impact which stripped away the mantle, leaving behind a large iron core. Or maybe the exoplanet is a remnant of a Neptune or super-Earth sized gaseous planet, where the atmosphere of the planet has completely blown away as the planet is blasted by a large amount of radiation from the star," Lam said.

(With inputs from agencies)