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An incredibly hot Earth-sized planet has been discovered orbiting a dwarf star 339 million light years away, scientists revealed.

The far-flung exoplanet - a term used for planets outside of our solar system - has a similar density to Mercury, astronomers said.

Named K2-229b, the metallic planet is just 20 per cent larger than Earth but has a mass more than double the size.

With a daytime temperature of 2000C, the planet tightly orbits a medium-sized star in the constellation of Virgo once every fourteen hours.

Astronomers from the University of Warwick, in partnership with researchers at Aix-Marsellie Universite in France and the Universidade de Porto, used NASA's Kepler telescope to discover and categorise K2-229b.

The "planet-hunting" Kepler spacecraft is currently on the K2 mission to discover exoplanets.

Researchers could detect the planet due to dips in the light from its host star as it orbited, periodically blocking starlight.

They then calculated the size, position and mass of K2-229b by measuring how much the starlight "wobbles" during orbit, due to the gravitational tug from the planet, which changes depending on the planet’s size.

The dense, metallic make-up of the plent could be due to its atmosphere having been eroded by intense wind and flares emitted by the nearby star, scientists said.

Or the planet may have been formed after a huge collision between two giant astronomical bodies in space billions of years ago.

Dr David Armstrong from the University of Warwick’s Astronomy and Astrophysics Group, commented: “Mercury stands out from the other Solar System terrestrial planets, showing a very high fraction of iron and implying it formed in a different way.

"We were surprised to see an exoplanet with the same high density, showing that Mercury-like planets are perhaps not as rare as we thought."