CoRoT-7c is an extrasolar planet which orbits the G-type main sequence star CoRoT-7, located approximately 489 light years away in the constellation Monoceros. It is either a super-Earth or a Neptune-like planet, orbiting at 0.046 AU from the star, taking 3.7 days or 89 hours to make one round trip around the star.
| Discovery | |
|---|---|
| Discovered by | Queloz et al. |
| Discovery site | La Silla Observatory, Chile |
| Discovery date | August 24, 2009 |
| Radial Velocity (HARPS) | |
| Orbital characteristics | |
| 0.046 AU (6,900,000 km)[1] | |
| Eccentricity | 0 |
| 3.698 ± 0.003[1] d | |
| Semi-amplitude | unknown[1] |
| Star | CoRoT-7 |
| Physical characteristics | |
| Mass | 13.289±0.689[2] ME |
Discovery
editThe discovery of the planet was announced in February 2009, during the First Corot Symposium. It was discovered during the follow-up started in order to confirm the existence of CoRoT-7b, a super-Earth uncovered by the CoRoT mission. However, unlike CoRoT-7b, it was not detected by the transit method from the CoRoT satellite, but only by the radial velocity method using HARPS from La Silla Observatory, Chile. A posteriori search of transits of CoRoT-7c in the lightcurve of the star CoRoT-7 yielded a negative result, confirming the planet is not transiting. As a consequence no radius measurement is available, and no density and structure models of the planet can be established.
Characteristics
editLike CoRoT-7b, the mass of CoRoT-7c is weakly constrained, since the radial velocity data is noisy due to the presence of stellar activity. Published mass measurements range from 8.4 Earth masses[1] to 13.5 Earth masses,[3] passing through 12.4 Earth masses[4] and 13.1 Earth masses.[5] This mass range encompasses the Super-Earths to Neptunes transition, so the nature of CoRoT-7c, either a rocky planet or an ice giant, remains unclear. However, if the larger mass estimates are correct, CoRoT-7c is probably a hot Uranus-like planet. Chances are high that planet's rotation is tidally locked to the orbital period, with one side of the planet always facing the star CoRoT-7 and the other one in permanent darkness.
A third planet, CoRoT-7d, is present in the system. Strong mutual gravitational forces could be exchanged between these planets, leading to powerful tidal forces.
Doubts about existence
editA published study[6] cast doubt on CoRoT-7c's existence, arguing that the combined presence of stellar activity and additional errors on HARPS radial velocity measurements preclude a meaningful search for additional companions besides CoRoT-7b. However, all the other studies seem to confirm the planet's existence: the signal in the HARPS data of CoRoT-7c is detected in analysis of different type, does not seem to be correlated with stellar activity and is stronger than the signal associated with the confirmed CoRoT-7b. The remarkable stability and precision showed by the HARPS spectrograph[7] also speaks in favour of the detection. The status of CoRoT-7c seems very well confirmed.
References
edit- ^ a b c d Queloz, D.; Bouchy, F.; Moutou, C.; Hatzes, A.; Hebrard, G.; Alonso, R.; Auvergne, M.; Baglin, A.; Barbieri, M.; Barge, P.; Benz, W.; Bordé, P.; Deeg, H.; Deleuil, M.; Dvorak, R.; Erikson, A.; Ferraz Mello, S.; Fridlund, M.; Gandolfi, D.; Gillon, M.; Guenther, E.; Guillot, T.; Jorda, L.; Hartmann, M.; Lammer, H.; Léger, A.; Llebaria, A.; Lovis, C.; Magain, P.; Mayor, M.; Mazeh, T.; Ollivier, M.; Pätzold, M.; Pepe, F.; Rauer, H.; Rouan, D.; Schneider, J.; Segransan, D.; Udry, S. & Wuchterl, G. (2009). "The CoRoT-7 planetary system: two orbiting Super-Earths" (PDF). Astronomy and Astrophysics. 506 (1): 303–319. Bibcode:2009A&A...506..303Q. doi:10.1051/0004-6361/200913096. Also available from exoplanet.eu Archived 2012-01-11 at the Wayback Machine
- ^ John, Ancy Anna; Collier Cameron, Andrew; Wilson, Thomas G. (2022-09-01). "The impact of two non-transiting planets and stellar activity on mass determinations for the super-Earth CoRoT-7b". Monthly Notices of the Royal Astronomical Society. 515 (3): 3975–3995. arXiv:2206.14216. Bibcode:2022MNRAS.515.3975J. doi:10.1093/mnras/stac1814. ISSN 0035-8711.
- ^ Ferraz-Mello; Tadeu dos Santos; Beauge; Michtchenko; Rodriguez (2010). "On planetary mass determination in the case of super-Earths orbiting active stars. The case of the CoRoT-7 system". Astronomy. 531: A161. arXiv:1011.2144. Bibcode:2011A&A...531A.161F. doi:10.1051/0004-6361/201016059. S2CID 55422304.
- ^ Hatzes; Dvorak; Wuchterl; Guterman; Hartmann; Fridlund; Gandolfi; Guenther; Paetzold (2010). "An Investigation into the Radial Velocity Variations of CoRoT-7". Astronomy and Astrophysics. 520: A93. arXiv:1006.5476. Bibcode:2010A&A...520A..93H. doi:10.1051/0004-6361/201014795. S2CID 38803450.
- ^ Léger, A.; Grasset, O.; Fegley, B.; Codron, F.; Albarede, A. F.; Barge, P.; Barnes, R.; Cance, P.; Carpy, S.; Catalano, F.; Cavarroc, C.; Demangeon, O.; Ferraz-Mello, S.; Gabor, P.; Grießmeier, J. -M.; Leibacher, J.; Libourel, G.; Maurin, A. -S.; Raymond, S. N.; Rouan, D.; Samuel, B.; Schaefer, L.; Schneider, J.; Schuller, P. A.; Selsis, F.; Sotin, C. (2011). "The extreme physical properties of the CoRoT-7b super-Earth". Icarus. 213 (1): 1. arXiv:1102.1629. Bibcode:2011Icar..213....1L. doi:10.1016/j.icarus.2011.02.004. S2CID 55348462.
- ^ Frederic Pont; Suzanne Aigrain; Shay Zucker (2010). "Re-assessing the radial-velocity evidence for planets around CoRoT-7". Monthly Notices of the Royal Astronomical Society. 411 (3): 1953–1962. arXiv:1008.3859. Bibcode:2011MNRAS.411.1953P. doi:10.1111/j.1365-2966.2010.17823.x. S2CID 118544414.
- ^ ""First Light" for HARPS at la Silla - Advanced Planet-Hunting Spectrograph Passes First Tests with Flying Colours".