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CoRoT-3b

Size comparison of CoRoT-3b with Jupiter.
Discovery
Discovered by	Deleuil et al. (CoRoT)
Discovery date	February 3, 2008
Detection method	Transit method
Orbital characteristics
Semi-major axis	0.057 ± 0.003 AU (8,530,000 ± 450,000 km)
Eccentricity	0
Orbital period (sidereal)	4.25680 ± 0.000005 d
Inclination	85.9 ± 0.8
Star	CoRoT-3
Physical characteristics
Mean radius	1.01 ± 0.07 RJ
Mass	21.66 ± 1.0 MJ
Mean density	26.4 ± 5.6 g/cm
Surface gravity	525 ± 85 m/s (1,720 ± 280 ft/s) 53.6 ± 8.7 g

CoRoT-3b (formerly known as CoRoT-Exo-3b) is a brown dwarf or massive extrasolar planet with a mass 21.66 times that of Jupiter. The object orbits an F-type star in the constellation of Aquila. The orbit is circular and takes 4.2568 days to complete. It was discovered by the French-led CoRoT mission which detected the dimming of the parent star's light as CoRoT-3b passes in front of it (a situation called a transit).

Physical properties

The mass of CoRoT-3b was determined by the radial velocity method, which involves detecting the Doppler shift of the parent star's spectrum as it moves towards and away from Earth as a result of the orbiting companion. This method usually gives only a lower limit on the object's true mass: the measured quantity is the true mass multiplied by the sine of the inclination angle between the normal vector to the orbital plane of the companion and the line of sight between Earth and the star, an angle which in general is unknown. However, in the case of CoRoT-3b, the transits reveal the inclination angle and thus the true mass can be determined. In the case of CoRoT-3b, the mass is 21.66 times the mass of the planet Jupiter.

As CoRoT-3b is a transiting object, its radius can be calculated from the amount of light blocked when it passes in front of the star and an estimate of the stellar radius. When CoRoT-3b was originally discovered, it was believed to have a radius significantly smaller than that of Jupiter. This would have implied it had properties intermediate between those of planets and brown dwarfs. Later more detailed analysis revealed that the object's radius is similar to that of Jupiter, which fits with the expected properties of a brown dwarf with the mass of CoRoT-3b.

The mean density of CoRoT-3b is 26,400 kg/m, greater than that of osmium under standard conditions. This high density is reached because of the extreme compression of matter in the object's interior: in fact, the radius of CoRoT-3b is in agreement with predictions for an object composed mainly of hydrogen. The surface gravity is correspondingly high, over 50 times the gravity felt at the surface of the Earth.

A later study called this density into question using data from Gaia data release 2, arriving at a lower density of 17300±2900 kg/m, but finding the exoplanet KELT-1b to be denser at 23700±4000 kg/m.

The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is mildly misaligned with the rotational axis of the star, misalignment equal to 37.6
_−22.3°.

Classification

The issue of whether CoRoT-3b is a planet or a brown dwarf depends on the definition chosen for these terms. According to one definition, a brown dwarf is an object capable of fusing deuterium, a process which occurs in objects more massive than 13 times Jupiter's mass. According to this definition, which is the one adopted by the International Astronomical Union's Working Group on Extrasolar Planets, CoRoT-3b is a brown dwarf. However, some models of planet formation predict that planets with masses up to 25–30 Jupiter masses can form via core accretion. If this formation-based distinction between brown dwarfs and planets is used, the status of CoRoT-3b becomes less clear as the method of formation for this object is not known. The issue is clouded further by the orbital properties of the object: brown dwarfs located close to their stars are rare (a phenomenon known as the brown-dwarf desert), while the majority of the known massive close-in planets (for example XO-3b, HAT-P-2b and WASP-14b) are in highly eccentric orbits, in contrast to the circular orbit of CoRoT-3b.

References

1. Schneider, J. "Notes for star CoRoT-3". Extrasolar Planets Encyclopaedia. Archived from the original on 2012-05-05. Retrieved 2009-03-27.
2. ^ Deleuil, M.; et al. (2008). "Transiting exoplanets from the CoRoT space mission. VI. CoRoT-Exo-3b: the first secure inhabitant of the brown-dwarf desert". Astronomy and Astrophysics. 491 (3): 889–897. arXiv:0810.0919. Bibcode:2008A&A...491..889D. doi:10.1051/0004-6361:200810625. S2CID 8944836.
3. Schneider, J. (2009-03-10). "Change in CoRoT planets names". Exoplanets (Mailing list). Archived from the original on 2010-01-18. Retrieved 2009-03-19.
4. "Exoplanet hunt update" (Press release). ESA. 2008-05-28. Retrieved 2009-03-27.
5. Schneider, J. (2008-05-19). "3 CoRoT transiting objects". Exoplanets (Mailing list). Retrieved 2009-03-27.
6. "CoRoT discovery stirs exoplanet classification rethink" (Press release). ESA. 2008-10-06. Retrieved 2009-03-27.
7. Baraffe, I.; et al. (2003). "Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458". Astronomy and Astrophysics. 402 (2): 701–712. arXiv:astro-ph/0302293. Bibcode:2003A&A...402..701B. doi:10.1051/0004-6361:20030252. S2CID 15838318.
8. Johns, Daniel; Marti, Connor; Huff, Madison; McCann, Jacob; Wittenmyer, Robert A.; Horner, Jonathan; Wright, Duncan J. (14 August 2018). "Revised Exoplanet Radii and Habitability Using Gaia Data Release 2". The Astrophysical Journal Supplement Series. 239 (1): 14. arXiv:1808.04533. Bibcode:2018ApJS..239...14J. doi:10.3847/1538-4365/aae5fb. S2CID 119503072.
9. Albrecht, Simon; Winn, Joshua N.; Johnson, John A.; Howard, Andrew W.; Marcy, Geoffrey W.; Butler, R. Paul; Arriagada, Pamela; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B.; Hirano, Teruyuki; Bakos, Gaspar; Hartman, Joel D. (2012), "Obliquities of Hot Jupiter Host Stars: Evidence for Tidal Interactions and Primordial Misalignments", The Astrophysical Journal, 757 (1): 18, arXiv:1206.6105, Bibcode:2012ApJ...757...18A, doi:10.1088/0004-637X/757/1/18, S2CID 17174530
10. "Definition of a "Planet"". Working Group on Extrasolar Planets (WGESP) of the International Astronomical Union. Archived from the original on 2012-07-02. Retrieved 2009-03-27.
11. Mordasini, C.; et al. (2007). "Giant Planet Formation by Core Accretion". arXiv:0710.5667v1 .

External links

Media related to COROT-3b at Wikimedia Commons

v t e Constellation of Aquila
Aquila in Chinese astronomy Smith's Cloud List of stars in Aquila
Stars	Bayer α (Altair) β (Alshain) γ (Tarazed) δ ε ζ (Okab) η θ (Tseen Foo) ι κ λ μ ν ξ (Libertas) ο π σ τ υ φ χ ψ ω ω A b c d e f g h i k l Flamsteed 4 5 7 8 10 11 18 19 20 21 22 23 24 42 45 46 51 56 57 58 62 64 66 68 69 70 14 Sge 62 Ser 64 Sgr Variable R U V W TT FF QS V368 V450 V500 V603 V604 V605 V606 V923 V1286 V1291 V1298 V1302 V1315 V1333 V1339 V1427 V1428 V1429 V1472 V1487 V1494 V1654 V1672 V1691 V1703 (Phoenicia) V1828 V1936 HR 7099 7143 7288 7300 7307 7396 7456 7569 7598 7599 7693 7717 7803 HD 179079 183263 187734 192699 (Chechia) Other CoRoT-2 CoRoT-3 CoRoT-8 Gaia BH3 HAT-P-41 PSR J1856+0245 PSR J1903+0327 PSR B1913+16 (Hulse–Taylor) PSR J1951+1123 SGR 1900+14 SS 433 W43A W49-2 WASP-80 (Petra) WD J1953−1019 ZTF J1901+1458
Exoplanets CoRoT-2b CoRoT-3b CoRoT-8b CoRoT-10b HD 179079 b HD 183263 b c HD 192263 b HD 192699 b ξ Aquilae b
Star clusters NGC 6709 NGC 6738 NGC 6755 NGC 6756 NGC 6760
Nebulae	NGC 6741 6751 6778 6781 6790 Other Abell 48 Abell 70 E Nebula Hen 2-428 HESS J1857+026 W43 W49 W49B W50
Galaxies	NGC 6814 Other IC 1327
Category

• Brown dwarfs
• Aquila (constellation)
• Transiting exoplanets
• Hot Jupiters
• Exoplanets discovered in 2008
• Exoplanets discovered by CoRoT