A ‘Heart of Diamonds’ for UK and US astronomers who find Carbon-rich Planet

Posted on 09 December 2010

A team of UK and US astronomers, including members of Keele University’s astrophysics group, has found the first carbon-rich planet, orbiting a star 1200 light years away, which could have an interior abundant in diamonds. Unlike Earth, which is rich in oxygen and has much smaller quantities of carbon, the planet WASP-12b is abundant in carbon and depleted in oxygen. The finding points to the existence of planets with compositions very different from those of our own Solar System.
The planet was originally found last year by the Wide-Angle Search for Planets (WASP) project, the UK's leading team of planet discoverers. Now a team of astronomers led by Nikku Madhusudhan of the Massachusetts Institute of Technology, have observed WASP-12b with NASA's Spitzer Space Telescope, and found that its atmosphere is dominated by molecules containing carbon. Keele astronomers Professor Coel Hellier, Dr Pierre Maxted and David Anderson are co-authors on the paper, published this week in Nature.  

"This is new territory and will motivate researchers to study what carbon-rich planets are made of", said lead author of the Nature paper, Nikku Madhusudhan. Although WASP-12b is a hot, Jupiter-sized ‘gas giant’ planet that would not have a surface, smaller rocky planets could also form in such planetary systems. “A rocky planet in such a planetary system could have an interior abundant in diamonds and a surface littered with graphite and diamonds”, said Professor Joe Harrington, of the University of Central Florida, who led the analysis of the Spitzer data. “The theorists will have fun with this one”. Could life thrive in such an environment, with little oxygen or water? That might not be so far-fetched given last week's announcement by NASA of bacteria that can survive by using arsenic in place of phosphorus, previously thought to be essential. 

WASP-12b is the size of Jupiter and among the hottest planets known, orbiting its star in only 26 hours. “Because WASP-12b is so close to its star and so hot”, explains Professor Coel Hellier of Keele University, “ the Spitzer Space Telescope can detect the heat of the planet, and studying this radiation tells us which molecules are in its atmosphere.” 

Earth is typical of Solar-System planets in having more oxygen than carbon. The Earth is mainly iron, oxygen and silicon, with silica — sand — being the commonest mineral.  WASP-12b is the first planet found where the oxygen/carbon ratio is reversed. The oxygen/carbon ratio of WASP-12b was deduced by analysing its infrared spectrum with Spitzer, and comparing the absorption features caused by carbon-rich molecules such as methane with those caused by water.   “The UK's WASP project has found over 40 planets orbiting other stars”, says David Anderson, of Keele University, “allowing us to select the ones that are hottest and thus best for studying with Spitzer's thermal cameras”. 

Image: An artist's conception of the hot carbon-rich planet WASP-12b orbiting closely around its host star (credit: NASA/JPL-Caltech/R. Hurt (SSC))
Notes to Editors

The Nature paper's  full title is ‘A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b’ Nikku Madhusudhan et al, DOI is 10.1038/nature09602. The paper will be published online at www.nature.com/nature on 08 December at 1800 GMT.


Prof. Coel Hellier
Keele University
+44 (0)1782 734243
+44 (0)7817 182867

Further Information

The WASP project ("Wide Angle Search for Planets") is a consortium of UK universities, funded by STFC, and including the Universities of St. Andrews, Leicester and Keele, and the Queen's University Belfast.  Having now found over 40 extra-solar planets transiting (passing in front of) their host star, WASP is currently the world's most successful search for transiting extra-solar planets.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer.

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Chris Stone,
Press Office,
Keele University.
Tel.: 01782 733375