HAT-P-2b
| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
 |
||
| Parent star | ||
| Star | HD 147506 | |
| Constellation | Hercules | |
| Right ascension | (α) | 16h 20m 36s |
| Declination | (δ) | +41° 02′ 53″ |
| Distance | 440 ± 52 ly (135 ± 16 pc) |
|
| Spectral type | F8V | |
| Orbital elements | ||
| Semimajor axis | (a) | 0.0677+0.0011-0.0017[1] AU |
| Eccentricity | (e) | 0.5163+0.0025-0.0023[1] |
| Orbital period | (P) | 5.63341±0.00013 days[1] d |
| Inclination | (i) | 90+0.85-0.93[1]° |
| Argument of periastron |
(ω) | 189.921.06-1.2[1]° |
| Time of periastron | (T0) | 2,454,213.4794+0.0053-0.003[1] JD |
| Semi-amplitude | (K) | 885±37 m/s |
| Physical characteristics | ||
| Mass | (m) | 8.65+0.39-0.55[1] MJ |
| Radius | (r) | 1.157+0.073-0.092 RJ |
| Density | (ρ) | 12500+2.6-3.6[1] kg m-3 |
| Surface gravity | (g) | 235.5 m/s² (24.01 g) |
| Temperature | (T) | 1187[2] K |
| Discovery information | ||
| Discovery date | 2007-05-02 | |
| Discoverer(s) | HATNet Project | |
| Detection method | Transit | |
| Discovery status | Published | |
HAT-P-2b is an extrasolar planet detected by the HATNet Project in May 2007. It orbits a class F star, (bigger and hotter than the Sun), located about 440 light-years away in the constellation Hercules. Every 5 days 15 hours, it crosses directly in front of the star as viewed from Earth.[3][4]
Contents |
[edit] Orbit and mass
The planet's mass has been estimated to be 8.65 times that of Jupiter, while its radius, at 135,978 km (84,493 mi), is 0.951 times Jupiter's. Its small size, despite the bloating of planet's atmosphere, is caused by the strong gravity of the planet. This indicates its mean density is twice that of Earth and its surface gravity approximately 24 times that on Earth, almost equal to the Sun. The orbit is very eccentric, ranging from 4.90 million to 15.36 million miles from the star.[3]
In addition to heat from its primary star, tidal heating is thought to have played a significant role in this planet's evolution.[5]
[edit] Rotation
As of August 2008, the most recent calculation of HAT-P-2b's Rossiter-McLaughlin effect and so spin-orbit angle was that of Winn in 2007 but Loeillet has in 2008 disputed it.[6] For Winn this is +1 ± 13 degrees.[7]
It has been suggested that there is a second outer planet perturbing HAT-P-2 b. This has not so far been proved or disproved.[3]
[edit] References
- ^ a b c d e f g h B. Loeillet, A. Shporer, F. Bouchy, F. Pont, T. Mazeh, J. L. Beuzit, I. Boisse, X. Bonfils, R. Da Silva, X. Delfosse, M. Desort, A. Ecuvillon, T. Forveille, F. Galland, A. Gallenne, G. Hébrard, A.-M. Lagrange, C. Lovis, M. Mayor, C. Moutou, F. Pepe, C. Perrier, D. Queloz, D. Ségransan, J. P. Sivan, N. C. Santos, Y. Tsodikovich, S. Udry, and A. Vidal-Madjar (2008). journal=Astronomy & Astrophysics Refined parameters and spectroscopic transit of the super-massive planet HD 147506b. 481. pp. 529–533. http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/abs/2008/14/aa8167-07/aa8167-07.html journal=Astronomy & Astrophysics. Retrieved 2008-03-27.
- ^ Ravilious, Kate (May 3, 2007). ""Weird" New Planet Weighs as Much as 2,500 Earths". National Geographic News. http://news.nationalgeographic.com/news/2007/05/070503-new-planet.html. Retrieved 2007-05-04.
- ^ a b c "Astronomers find super-massive planet" (Press release). Harvard-Smithsonian Center for Astrophysics. May 2, 2007. http://www.cfa.harvard.edu/press/2007/pr200711.html.
- ^ Bakos et al.; Kovacs, G.; Torres, G.; Fischer, D. A.; Latham, D. W.; Noyes, R. W.; Sasselov, D. D.; Mazeh, T. et al (2007). "HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star". The Astrophysical Journal 670 (1): 826–832. Bibcode 2007ApJ...670..826B. doi:10.1086/521866. http://www.iop.org/EJ/article/0004-637X/670/1/826/71995.html.
- ^ Jackson, Brian; Richard Greenberg, Rory Barnes (2008). "Tidal Heating of Extra-Solar Planets". ApJ 681 (2): 1631. arXiv:0803.0026. Bibcode 2008ApJ...681.1631J. doi:10.1086/587641.
- ^ Joshua N. Winn (2008). "Measuring accurate transit parameters". Proceedings of the International Astronomical Union 4: 99. arXiv:0807.4929v2. doi:10.1017/S174392130802629X. Loeillet et al.; Shporer, A.; Bouchy, F.; Pont, F.; Mazeh, T.; Beuzit, J. L.; Boisse, I.; Bonfils, X. et al (2008). "Refined parameters and spectroscopic transit of the super-massive planet HD 147506b". A&A 481 (2): 529. Bibcode 2008A&A...481..529L. doi:10.1051/0004-6361:20078167.
- ^ Winn et al. (2007). Astrophysical Journal (Letters) 665: L167.
[edit] External links
Media related to HAT-P-2b at Wikimedia Commons
