Geneva researchers have determined the weight and density of the scorching hot Corot-7b, the smallest known planet outside our solar system

An international team led by Geneva University's Didier Queloz, says that the planet is made of rock, just like the Earth, although its radius is 80 per cent larger. It is five times heavier.

It is the first rocky exosolar planet.

Queloz describes the planet as "Dante's Inferno". Its hot side is nearly 2,000 Celsius and it orbits its sun every 20 hours at a speed of 750,000 km/h.

The findings are published in the journal Astronomy & Astrophysics.

Mercury, the planet nearest to the Earth's sun, takes 88 days to circle the sun.

Corot-7b was discovered this year. European scientists have watched it dozens of times to measure its density to prove that it is rocky, like Earth. It is in Earth's general neighbourhood, circling a star in the winter sky about 500 light years away. Each light year is about 9.7 trillion kilometres.

Scientists have found more than 300 planets outside the solar system but all have been gas balls or cannot be proved to be solid.

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