December 3, 2010. Copyright 2010, Graphic News. All rights reserved

Super-Earth is a hot, steamy planet

LONDON, December 3, Graphic News: Astronomers have for the first time analysed the atmosphere of a “super-Earth”, the name given to a distant, Earth-like planet outside our solar system, according to research published in the December 2 issue of Nature.

The breakthrough is a key step in the quest to identify so-called exoplanets that could potentially host forms of life we might recognise, the researchers said. The exoplanet in question, dubbed GJ1214b, is some 42 light years -- 400 trillion kilometers, (250 trillion miles) -- from our corner of the Milky Way.

Discovered last year, GJ1214b circles a small, faint sun, enabling researchers to analyse its light spectrum as it passes in front of, and is backlit by its star. The measurements provide an unprecedented glimpse of the atmosphere of a relatively small planet.

“This is the most accessible way to study these planets' atmospheres,” says lead study author Jacob Bean of the Harvard-Smithsonian Centre for Astrophysics. “The light from the host star passes through part of the atmosphere, and the chemical species imprint their signature on the light.”

While most of the 700-plus exoplanets discovered to date are behemoths -- more massive than Jupiter -- GJ1214b is just 6.5 times the mass of our own planet. It is the second exoplanet (after COROT-7b) discovered to have a mass and radius similar to the Earth.

Using the European Space Agency’s Very Large Telescope in Chile, Bean and his colleagues took advantage of a favourable planetary alignment to measure the spectrum of GJ1214b.

Three theories had evolved on what the atmosphere contained. One held that it was mostly hydrogen gas, but the spectrographic data did not show hydrogen. Another suggested that it was indeed hydrogen but that this was masked by a cloudy haze of some kind. While the scientists acknowledged this as a possibility, they could identify “no candidate” for what the clouds might be.

The third theory held that GJ1214b is shrouded by water which -- given the nearness to its star -- would be in the form of steam.

Exoplanets are being discovered on an almost daily rate since NASA’s Kepler orbiting observatory was launched in March last year. Kepler is designed to spot Earth-sized planets, ones that might orbit their sun-like stars in the “Goldilocks” zone, not so close as to be overly hot and not so far away as to leave the planet too cold for habitation.

“If we can find these kinds of planets, we’re going to have the facilities available in the next decade to study them in detail,” Professor Bean says. Being able to detect an exoplanet’s atmosphere is a great step forward. The next step is to look for signs of biological activity -- for signs of life.
/ENDS