Astronomers discover 'waterworld,' a brand new planet type

Astronomers have discovered an extremely hot, steamy world with far more water than Earth, which they are callinga completely new type of planet.

GJ1214b is the first "waterworld" ever described by astronomers. The planet was first found in 2009, but astronomers previouslyassumed that its hazy exterior masked a gaseous core, like other bodies in the solar system.

Now, however, apaper detailing the planet's newly uncoveredqualities has been published online and accepted for publication in the Astrophysical Journal.

The planet is located 40 light years from Earth in the constellation Ophiuchus. It has a diameter 2.7 times larger than Earth and a mass that is seven times greater.

It circles a red dwarf star cooler and smaller than the sun, but is just two million kilometres away from its star, completing an orbit every 38 hours. In contrast, Mercury, the nearest planet to the sun in our solar system, orbits an average of 58 million kilometres away and takes 88 days to complete each circuit.

GJ1214b's star-hugging orbit gives it a sizzling surface temperature of 230 C, transforming the water into states that don't exist on Earth.

"The high temperatures and high pressures would form exotic materials like 'hot ice' or 'superfluid water', substances that are completely alien to our everyday experience," said Zachory Berta, the lead author of the study, in a statement.

The researchers used a camera on the Hubble space telescope to peer through the planet's atmosphere as it crossed in front of its star.

Different chemicals in the atmosphere filter the light in different ways and information about the chemical composition can be teased out by comparing the intensity of different colours of starlight that has passed through the planet's atmosphere to the colour of the starlight that hasn't passed through.

The resulting data, combined with known information about the planet, suggested GJ1214b's atmosphere is at least 50 per cent water by mass.

The researchers think the planet originally formed farther away from the star in an area with lots of water andice and later moved in to where it is now. Along the way, it would have passed through the "habitable zone," with temperatures similar to Earth's.