CoRoT-7
CoRoT-7 (TYC 4799-1733-1) is a binary star system. The primary, CoRoT-7A is a G-type main sequence star, slightly smaller, cooler, and younger than the Sun. It has an apparent magnitude of 11.67, fainter than Proxima Centauri (mag. 11.05), the nearest star to the Sun. This star is approximately 520 light-years away from the Solar System[2] in the constellation Monoceros (the Unicorn).[5]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Monoceros[1] |
| Right ascension | 06h 43m 49.4688s[2] |
| Declination | −01° 03′ 46.817″[2] |
| Apparent magnitude (V) | 11.668[1] |
| Characteristics | |
| CoRoT-7A | |
| Spectral type | G9V[1] |
| CoRoT-7B | |
| Spectral type | M4V[3] |
| Astrometry | |
| Radial velocity (Rv) | +31.174 ± 0.0086[1] km/s |
| Proper motion (μ) | RA: 10.984[2] mas/yr Dec.: -0.040[2] mas/yr |
| Parallax (π) | 6.2676 ± 0.0139 mas[2] |
| Distance | 520 ± 1 ly (159.6 ± 0.4 pc) |
| Absolute magnitude (MV) | 5.78[1] |
| Position (relative to CoRoT-7A)[3] | |
| Component | CoRoT-7B |
| Epoch of observation | 2021 |
| Angular distance | 75.7″ |
| Observed separation (projected) | 12160 AU |
| Details | |
| CoRoT-7A | |
| Mass | 0.91 ± 0.03[1] M☉ |
| Radius | 0.82 ± 0.04[1] R☉ |
| Surface gravity (log g) | 4.47 ± 0.10[1] cgs |
| Temperature | 5250 ± 60[1] K |
| Metallicity | [M/H] = 0.12 ± 0.06[1] |
| Rotation | ~23 days[4] |
| Rotational velocity (v sin i) | <3.5[1] km/s |
| Age | (1.2–2.3) × 109[1] years |
| CoRoT-7B | |
| Mass | 0.23[3] M☉ |
| Other designations | |
2MASS J06434947-0103468, TYC 4799-1733-1, GSC 04799-01733 | |
| CoRoT-7A: Gaia EDR3 3107267177757848576 | |
| CoRoT-7B: Gaia EDR3 3107267212116737792 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| Extrasolar Planets Encyclopaedia | data |
The comoving companion CoRoT-7B was discovered in 2021. It is a red dwarf star.[3]
Location and properties
The star is located in the LRa01 field of view of the CoRoT spacecraft. It is about 500 light years from Earth. According to the project website, this field is in the Monoceros constellation.[5] Published data[6] lists the stellar properties as being a G9V yellow dwarf with a temperature of 5250 K, a radius of about 82% of the Sun and a mass of about 91% of the Sun.[1] But other sources have listed it as a (K0V) orange dwarf.[7] The metallicity is 0.12 ± 0.06. The star is estimated to be about 150 parsecs away and with an age in the range 1.2 – 2.3 billion years, is younger than our own star which has an age of 4.6 billion years.[1] The rotation period of the star, inferred by the lightcurve obtained by CoRoT, is around 23 days.
Planetary system
The primary star is orbited by the super-Earth exoplanets CoRoT-7b and CoRoT-7c, both discovered in 2009.[4] The existence of a possible third planet CoRoT-7d, detected in a published study,[8] remains unconfirmed and dubious.[9] The discovery of the inner planet was made using the transit method by the CoRoT program. CoRoT-7b is notable for its relatively small size, compared to other exoplanets known at the time.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | from 2.3 to 8.5 M🜨 | 0.0172 ± 0.00029 | 0.853585 ± 0.000024 | 0 | — | 1.58 ± 0.1 R🜨 |
| c | from 8.4 to 13.5[note 1] M🜨 | 0.046 | 3.698 ± 0.003 | 0 | — | — |
| d (unconfirmed) | 16.8[note 2] M🜨 | 0.08 | 9.021 ± 0.019 | 0 | — | — |
This star was reported to have stellar activity, making the confirmation process for CoRoT-7b more difficult. In fact, mass estimates are affected by large uncertainty due to stellar activity that perturbs the radial velocity measurements needed to "weigh" the planets.[4][11][9]
CoRoT-7d
CoRoT-7d is an unconfirmed exoplanet that has been hypothesized to orbit around CoRoT-7. This exoplanet was first claimed by A. P. Hatzes et al in 2010 by the radial velocity method.[8] The existence of CoRoT-7d is not definitively confirmed, and has been called into question - the radial velocity signal is more likely to be an artifact of the stellar rotation.[9]
If it exists, CoRoT-7d's mass would be 0.052 times Jupiter, but its volume and diameter are unknown. One year on CoRoT-7d would be equivalent to 9.021 days on Earth. Because of its closeness to its star, the exoplanet cannot be seen in a telescope; only its gravitational effect can be detected by the Doppler effect on its electromagnetic spectrum (radial velocity method).
Notes
- Assuming CoRoT-7b and CoRoT-7c are coplanar orbits.
- Assuming CoRoT-7b and CoRoT-7d are coplanar orbits.
References
- Léger, A; et al. (2009). "Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius". Astronomy and Astrophysics. 506 (1): 287–302. arXiv:0908.0241. Bibcode:2009A&A...506..287L. doi:10.1051/0004-6361/200911933. S2CID 5682749.
- Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
- The Census of Exoplanets in Visual Binaries: population trends from a volume-limited Gaia DR2 and literature search, 2021, arXiv:2101.12667
- Queloz, D.; Bouchy, F.; Moutou, C.; Hatzes, A.; Hebrard, G.; et al. (2009). "The CoRoT-7 planetary system: two orbiting Super-Earths" (PDF). Astronomy and Astrophysics. 506 (1): 303. Bibcode:2009A&A...506..303Q. doi:10.1051/0004-6361/200913096. Also available from exoplanet.eu
- Rouan; et al. (February 3, 2009). "CoRoT-exo-7b Has CoRoT discovered the first transiting Super-Earth around a main sequence star?" (PDF). CoRoT Symposium—Paris. Archived from the original (PDF) on July 20, 2011. Retrieved 2009-07-05.
- Bruntt; Deleuil; Fridlund; Alonso; Bouchy; Hatzes; Mayor; Moutou; Queloz (2010). "Improved stellar parameters of CoRoT-7". Astronomy and Astrophysics. 519: A51. arXiv:1005.3208. Bibcode:2010A&A...519A..51B. doi:10.1051/0004-6361/201014143. S2CID 54657440.
- Jean Schneider. "Star : CoRoT-7". The Extrasolar Planets Encyclopaedia. Retrieved 2009-12-26.
- 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.
- Haywood, R. D.; et al. (September 2014). "Planets and stellar activity: hide and seek in the CoRoT-7 system". Monthly Notices of the Royal Astronomical Society. 443 (3): 2517–2531. arXiv:1407.1044. Bibcode:2014MNRAS.443.2517H. doi:10.1093/mnras/stu1320. S2CID 23807689.
- "Super-Earth found! The smallest transiting extrasolar planet ever discovered". Paris Observatory. February 2009. Archived from the original on 2009-09-23. Retrieved 2009-02-04.
- "CoRoT-Exo-7b: Confirming the first transiting rocky planet". Archived from the original on 2011-09-29. Retrieved 2010-08-23.
External links
- Schilling, Govert (2009-02-03). "COROT Finds the Smallest Exoplanet Yet". Sky & Telescope. Archived from the original on 2009-02-07. Retrieved 2009-02-04.