The CoRoT (Convection, Rotation and Transits) spacecraft has been busy, and using this exoplanet-finding-machine astronomers recently found six new extrasolar planets, which contain an odd assortment of new worlds. They include shrunken-Saturns to bloated hot Jupiters, as well a rare brown dwarf with 60 times the mass of Jupiter. “Each of these planets is interesting in its own right, but what is really fascinating is how diverse they are,” said co-investigator Dr Suzanne Aigrain from Oxford University’s Department of Physics. “Planets are intrinsically complex objects, and we have much to learn about them yet.”
CoRoT is dedicated to looking for planets orbiting other stars, and finds them when they transit, or pass in front of their stars. CoRot now has found 15 of the total 461 exoplanets.
Once CoRoT detects a transit, additional observations are made from the ground, using a number of telescopes all over the world. Although astronomers cannot see the planets directly, they use the space- and ground-based data to measure the sizes, masses, and orbits of these new planets precisely. This is why, among all known exoplanets, those with transits yield the most complete information about planet formation and evolution.
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‘Every discovery of an extrasolar planetary system is a new piece in the puzzle of how these systems do form and evolve. The more systems we uncover, the better we can hope to understand the processes at play,’ said Magali Deleuil, researcher at the Laboratoire d’Astrophysique de Marseille (LAM) and head of the CoRoT exoplanet program.
The six new planets are:
CoRoT-8b: the smallest in this batch: At about 70% of the size and mass of Saturn, CoRoT-8b is moderately small among the previously known transiting exoplanets. Its internal structure should be similar to that of ice giants, like Uranus and Neptune, in the Solar System. It is the smallest planet discovered by the CoRoT team so far after CoRoT-7b, the first transiting Super-Earth.
CoRoT-10b: the eccentric giant: The orbit of CoRoT-10b is so elongated that the planet passes both very close to and very far away from its star. The amount of radiation it receives from the star varies tenfold in intensity, and scientists estimate that its surface temperature may increase from 250 to 600°C, all in the space of 13 Earth-days (the length of the year on CoRoT-10b).
CoRoT-11b: the planet whose star does the twist: CoRoT-11, the host star of CoRoT-11b, rotates around its axis in 40 hours. For comparison, the Sun’s rotation period is 26 days. It is particularly difficult to confirm planets around rapidly rotating stars, so this detection is a significant achievement for the CoRoT team.
CoRoT-12b, 13b and 14b: a trio of giants: These three planets all orbit close to their host star but have very different properties. Although CoRoT-13b is smaller than Jupiter, it is twice as dense. This suggests the presence of a massive rocky core inside the planet. With a radius 50% large than Jupiter’s (or 16 times larger than the Earth’s), CoRoT-12b belongs to the family of `bloated hot Jupiters’, whose anomalously large sizes are due to the intense stellar radiation they receive. On the other hand, CoRoT-14b, which is even closer to its parent star, has a size similar to Jupiter’s. It is also massive, 7.5 times the mass of Jupiter, which may explain why it is less puffed up. Such very massive and very hot planets are rare, CoRoT-14b is only the second one discovered so far.
CoRoT-15b: the brown dwarf: CoRoT-15b’s mass is about 60 times that of Jupiter. This makes it incredibly dense, about 40 times more so than Jupiter. For that reason, it is classified as a brown dwarf, intermediate in nature between planets and stars. Brown dwarfs are much rarer than planets, which makes this discovery all the more exciting.
Source: Oxford University