Hubble telescope takes a 'close' look at 'Super Earth' GJ1214b and discovers - clouds!

IT'S an alien planet 40-light-years away. Now Hubble has spent more time staring at it than any other. What it found is pushing the boundaries of exploration.

How GJ 1214b and GJ436b stack-up against Earth and Neptune.

IT'S an alien planet 'just' 40-light-years away. Now Hubble has spent more time staring at it than any other. What it found is pushing back the boundaries of exploration.

The planet - known as GJ1214b - is known as a "super-Earth" because of its large size and close orbits to their stars.

Very little is known about them. We know they're big. We know they're heavy. We know they're common.

We know there is nothing like them in our own solar system.

Now a team of astronomers have focused space telescope Hubble's eye on one of the closest known examples - and found clouds.

Earlier "looks" at GJ1214b produced several possible options for the planet's atmosphere.

It could have been almost entirely made of water vapour. Or it could have some kind of high-altitude cloud that blocked any observation of what lies beneath.

Hubble gazed at the infinitesimally small pinprick of light for a total of 96 hours over a period of 11 months.

"We really pushed the limits of what is possible with Hubble to make this measurement," the University of Chicago's Laura Kreidberg said. "This advance lays the foundation for characterising other Earths with similar techniques."

"I think it's very exciting that we can use a telescope like Hubble that was never designed with this in mind, do these kinds of observations with such exquisite precision, and really nail down some property of a small planet orbiting a distant star," explained the University of Chigaco's Jacob Bean.

GJ 1214b was chosen because it whizzes around its parent star every 38 hours, giving scientists an opportunity to study its atmosphere as starlight filters through it.

Using light from the near-infra-red light spectrum, the researchers found what they believe is definitive evidence of high-altitude clouds blanketing the planet.

How GJ 1214b and GJ436b stack-up against Earth and Neptune.

These clouds conceal what's going on beneath.

Astronomers still don't know what these clouds are made of.

"You would expect very different kinds of clouds to form than you would expect, say, on Earth," Kreidberg said.

The clouds could be made out of potassium chloride or zinc sulfide at the scorching temperatures of 230C found on GJ 1214b.

Exactly what the clouds are will not likely be known until after the launch of NASA's next major space telescope, the 6.5m James Webb Space Telescope later this decade.

A second team of researchers examined what is categorised as a "Warm Neptune". Only 36-light-years away, GJ436b is much closer to its star than Neptune is to our sun.

The spectra Hubble found was featureless; revealing no chemical fingerprints whatsoever.

Heather Knutson of the California Institute of Technology in Pasadena said: "Either this planet has a high cloud layer obscuring the view, or it has a cloud-free atmosphere that is deficient in hydrogen, which would make it very unlike Neptune.

"Both planets are telling us something about the diversity of planet types that occur outside of our own solar system; in this case we are discovering we may not know them as well as we thought," said Knutson. "We'd really like to determine the size at which these planets transition from looking like mini-gas giants to something more like a water world or a rocky, scaled-up version of the Earth. Both of these observations are fundamentally trying to answer that question."

Both studies appear in the January 2 issue of the journal Nature.