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European team finds smallest transiting extrasolar planet ever
February 03, 2009The CoRoT satellite has discovered a planet only twice as large as the Earth orbiting a star slightly smaller than the Sun. It is the smallest extrasolar planet (planet outside our solar system) whose radius has ever been measured. The planet's composition is not yet certain, but it is probably made predominantly of rock and water. It orbits its host star in 20 hours, which is the shortest orbital period of all exoplanets found so far. Astronomers infer its temperature must be so high (over 1000 degrees C) that it should be covered in lava or superheated water vapour.
Most of the 330 or so exoplanets discovered so far are giant planets, primarily composed of gas, like Jupiter and Neptune. This new object, named CoRoT-Exo-7b, is very different. "Finding such a small planet wasn't a complete surprise", says Dr Daniel Rouan, from LESIA in Paris, who announced the discovery today at a conference in Paris. Dr Alain Leger from the Institut d'Astrophysique de Marseille, leader of the discovery paper, explains: "It could be an example of a so-called ocean planet, whose existence was predicted some years ago: a Neptune-like planet, made of ice around a rocky core, drifts so close to its star, the ice the melting to form a fluid envelope."
Such a small planets such as this one is extremely difficult to detect. CoRoT-Exo-7b was found because it passes in front of its host star, causing the star to dim very slightly once per orbit - a so-called transit, which in this case is only 0.03% deep. "We were able to see it with CoRoT because it is in space, with no atmosphere to disturb the measurements or daylight to interrupt them." explains Dr Roi Alonso, from the Laboratoire d'Astrophysique de Marseille.
The team then had to make sure they were not seeing one of many other kinds of objects that can mimic planetary transits, using complementary observations from the ground. This is particularly challenging in the case of such a small planet, as Dr Aigrain from the University of Exeter explains "We ruled out every mimic except for a very improbable, almost perfect chance alignment of three stars. All our data so far is consistent with the transits being caused by a planet of a few Earth masses, though more data are needed for a precise mass estimate."
The discovery of CoRoT-Exo-7b is being announced today at the CoRoT Symposium 2009 in Paris and will be the published in a forthcoming special issue of the journal Astronomy and Astrophysics dedicated to results from CoRoT.
University of Exeter
The team then had to make sure they were not seeing one of many other kinds of objects that can mimic planetary transits, using complementary observations from the ground. This is particularly challenging in the case of such a small planet, as Dr Aigrain from the University of Exeter explains "We ruled out every mimic except for a very improbable, almost perfect chance alignment of three stars. All our data so far is consistent with the transits being caused by a planet of a few Earth masses, though more data are needed for a precise mass estimate."
The discovery of CoRoT-Exo-7b is being announced today at the CoRoT Symposium 2009 in Paris and will be the published in a forthcoming special issue of the journal Astronomy and Astrophysics dedicated to results from CoRoT.
University of Exeter
Extrasolar Planet Current Events and Extrasolar Planet News RSSCaltech scientists predict greater longevity for planets with life
Roughly a billion years from now, the ever-increasing radiation from the sun will have heated Earth into inhabitability; the carbon dioxide in the atmosphere that serves as food for plant life will disappear, pulled out by the weathering of rocks; the oceans will evaporate; and all living things will disappear.
NASA/University team develops new method to find alien oceans
NASA-sponsored scientists looking back at Earth with the Deep Impact/EPOXI mission have developed a method to indicate whether Earth-like alien (extrasolar) worlds have oceans.
New technique could find water on Earth-like planets orbiting distant suns
Since the early 1990s astronomers have discovered more than 300 planets orbiting stars other than our sun, nearly all of them gas giants like Jupiter.
Missing planets attest to destructive power of stars' tides
During the last two decades, astronomers have found hundreds of planets orbiting stars outside our solar system. New research indicates they might have found even more except for one thing - some planets have fallen into their stars and simply no longer exist.
Finding Twin Earths: Harder Than We Thought!
Does a twin Earth exist somewhere in our galaxy? Astronomers are getting closer and closer to finding an Earth-sized planet in an Earth-like orbit. NASA's Kepler spacecraft just launched to find such worlds.
Hubble finds carbon dioxide on an extrasolar planet
The NASA/ESA Hubble Space Telescope has discovered carbon dioxide in the atmosphere of a planet orbiting another star.
Hubble finds first organic molecule on extrasolar planet
The tell-tale signature of the molecule methane in the atmosphere of the Jupiter-sized extrasolar planet HD 189733b has been found with the Hubble Space Telescope. Under the right circumstances methane can play a key role in prebiotic chemistry - the chemical reactions considered necessary to form life as we know it.
Deep Impact extended mission heads for comet Hartley 2
NASA has given a University of Maryland-led team of scientists the green light to fly the Deep Impact spacecraft to Comet Hartley 2 on a two-part extended mission known as EPOXI. The spacecraft will fly by Earth on New Year's Eve at the beginning of a more than two-and-a-half-year journey to Hartley 2.
Hazy red sunset on extrasolar planet
A team of astronomers have used the NASA/ESA Hubble Space Telescope to detect, for the first time, strong evidence of hazes in the atmosphere of a planet orbiting a distant star. The discovery comes after extensive observations made recently with Hubble's Advanced Camera for Surveys (ACS).
The fine line between stability and instability -- when do gas giants reach the point of no return?
Planetary scientists at UCL have identified the point at which a star causes the atmosphere of an orbiting gas giant to become critically unstable, as reported in this week's Nature (December 6).
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