Possible water in the atmosphere of a super-Earth

Mar 05, 2012
The infrared spectrum of the super-Earth GJ1214b. The circles show the measured intensity at each wavelength; the bars show the uncertainties. Also plotted are some proposed model atmospheres - the best fitting ones contain water vapor. Credit: Zachory Berta, 2012

A "super-Earth" is an exoplanet (a planet around another star) whose mass is between about two and ten Earth-masses. Planets larger than this are closer to Uranus and Neptune in size (and perhaps in other physical properties as well). The category of "super-Earth" currently refers only to the mass of the object, and not to its radius, its orbital distance from the star, its surface temperature, or its atmospheric properties, although naturally astronomers are working hard to identify super-Earths that might offer clues about the Earth in these features. Of the 576 exoplanets whose basic parameters are currently approximately known, there are 36 in the super-Earth category.

Four CfA astronomers, Zachory Berta, David Charbonneau, Jean-Michel Desert, and Jonathan Irwin, together with six colleagues, used the to probe the atmosphere around the transiting super-Earth known as GJ1214b. This has a mass of 6.5 Earth-masses and a radius of 2.7 Earth-radii, and it orbits a small M-dwarf star (its diameter is only 21% of the Sun's). They used the Hubble to observe the planet as it transited across the face of the star; as it did so, the planet's atmosphere absorbed light from the star, thus subtly altering the star's intrinsic spectrum as we observe it. The intrinsic spectrum itself was carefully measured and subtracted after the transit.

Earlier models tried to predict what the atmosphere of this super-Earth might contain, based on ground-based transit spectra of it and on our current knowledge of the atmospheres of the planets in the solar system. For example, an atmosphere dominated by is one possibility; this is the situation in Jupiter. But measurements made in three separate transits found no evidence for this scenario - nor were they consistent with an equilibrium atmosphere composed of elements whose relative abundances are those of the average solar system. Instead, the astronomers concluded that, unless the atmosphere has a thick top layer of clouds obscuring our view, its probable composition includes abundant water vapor. Probing the atmosphere around a planet orbiting a star 42 light-years away is a remarkable achievement and an early step.

Future observations of this and other transiting exoplanets will tell us more about the atmospheres of exoplanets, and lead to a better understanding of how atmospheres form, evolve, and behave under a wide range of physical conditions.

Explore further: Astronomers: 'Tilt-a-worlds' could harbor life

Related Stories

Hunting for transits of Super-Earth GJ 581e

Jun 02, 2011

(PhysOrg.com) -- An international team of astronomers has ruled out transits of a water-rich or hydrogen-helium atmosphere planet for Gliese 581e. The host star itself is relatively quiet which means good ...

Water-Ice Super-Earths

Aug 27, 2010

A "super-Earth" is a planet around another star (an "exoplanet") whose mass is less than about ten times that of the Earth. Of the 480 or so extrasolar planets now known, most have masses larger than the mass ...

An Exoplanet with a Potassium-Rich Atmosphere

Mar 04, 2011

(PhysOrg.com) -- A hot Jupiter - a type of celestial object unknown only fifteen years ago - is a Jupiter-sized exoplanet orbiting so close to its host star that its atmospheric temperature is thought to be ...

Recommended for you

Astronomers: 'Tilt-a-worlds' could harbor life

13 hours ago

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, ...

Pushy neighbors force stellar twins to diverge

21 hours ago

(Phys.org) —Much like an environment influences people, so too do cosmic communities affect even giant dazzling stars: Peering deep into the Milky Way galaxy's center from a high-flying observatory, Cornell ...

Image: Multiple protostars within IRAS 20324+4057

Apr 14, 2014

(Phys.org) —A bright blue tadpole appears to swim through the inky blackness of space. Known as IRAS 20324+4057 but dubbed "the Tadpole", this clump of gas and dust has given birth to a bright protostar, ...

Research group to study interstellar molecules

Apr 11, 2014

From April 2014, a new group will study interstellar molecules and use them to explore the entire star and planet formation process at the Max Planck Institute for Extraterrestrial Physics. Newly appointed ...

Astronomers suggest more accurate star formation rates

Apr 10, 2014

(Phys.org) —Astronomers have found a new way of predicting the rate at which a molecular cloud—a stellar nursery—will form new stars. Using a novel technique to reconstruct a cloud's 3-D structure, ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Mar 07, 2012
The spectrum seems to have features not in the samples. So it likely has something else in it too. Need to refine the spectrum somewhat.

More news stories

Astronomers: 'Tilt-a-worlds' could harbor life

A fluctuating tilt in a planet's orbit does not preclude the possibility of life, according to new research by astronomers at the University of Washington, Utah's Weber State University and NASA. In fact, ...

NASA Cassini images may reveal birth of a Saturn moon

(Phys.org) —NASA's Cassini spacecraft has documented the formation of a small icy object within the rings of Saturn that may be a new moon, and may also provide clues to the formation of the planet's known ...

Vegetables on Mars within ten years?

The soil on Mars may be suitable for cultivating food crops – this is the prognosis of a study by plant ecologist Wieger Wamelink of Wageningen UR. This would prove highly practical if we ever decide to ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.