After almost one year and a half of observing, the harvest is rich for CoRoT. The satellite has now discovered 5 new exoplanets, and furthermore has detected a surprising object, intermediate between a planet and a brown dwarf. The object has a very small radius, and its density must be very high, derived from its mass of 20 Jupiters found from the ground. In addition, CoRoT has now found one of the smallest variation signal. If it is a transit, the planet’s radius would be 1.7 times the radius of the Earth.
Since 510 days, the CoRoT spacecraft and the telescope are working very well and observations continue as planned. Observations of the 6th field, with the third long 5 month non-stop simultaneous recording of 12000 stars, started earlier this month. At IAU Symposium 253 held this week in Cambridge Massachussets, CoRoT took the first opportunity to discuss CoRoT results with the specialists in extrasolar planets finding.
CoRoT announced three new discoveries at the meeting. Two new planets bring CoRoT total to 5. The presentation of a new type of object immediately caused debates in the CoRoT team and between the 200 international astronomers present at the meeting. This object, called CoRoT-exo-3b, is something between a brown dwarf and a planet. For a super planet its radius is very small. If it is stellar, it would be the smallest one. Follow-up observations from the ground have weighted it at 20 Jupiter mass. It is then denser than twice Platinum. So CoRoT, build to discover the smallest planets, now brings a new push to the discussion about what is a planet, by finding kind of a missing link between stars and planets.
Good news also on the side of finding small planets. CoRoT has picked up signals as small as 5 parts in ten thousand. If it is the transit, the planet’s radius would be 1.7 times the radius of the Earth.
Figure 1:Le plus petit signal détecté (à gauche) est agrandi dans la deuxieme figure (à droite). La nature planétaire n’est pas encore confirmée. Cliquer sur l’image pour l’agrandir [en]Figure : On this light curve one can immediately see a variety of variabilities and time scales. A periodic variation over approximately 1.5 days, A long term variation, producting a sort of beat phenomenon with a period of roughly 40 days. Let’s remark that the continuity of the observations over 120 days was necessary to detect this effect. These large scale variations are probably due to the rotation of the star, which has a non uniform surface (as seen on a smaller scale on the Sun), but it is too early to give a firm interpretation. very narrow spikes occurring regularly superimposed on top of this long term variations. They are the signature of a smaller body orbiting the star with a period of almost 5 days. The nature of this object ( a very big planet or a very small star) will be confirmed by follow-up observations on the ground. Click on the image to enlarge it
Reference
The CoRoT team, Communication at the Boston Conference, IAU Symposium 253.
