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Exoplanet Comparison HAT-P-2 b.png
Size comparison of HAT-P-2b with Jupiter.
Discovered byHATNet Project[1]
Discovery date2007-05-01[2]
Orbital characteristics
5.6334729±0.0000061 days[4] d
StarHD 147506
Physical characteristics
Mean radius
1.106±0.061[5] RJ
[3] MJ
Mean density
7300±1600 kg m−3
162±27 m/s²

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 420 light-years away in the constellation Hercules. Every 5 days 15 hours, it crosses directly in front of the star as viewed from Earth.[1][2]

Orbit and mass[edit]

The planet's mass has been estimated to be 8.65 times that of Jupiter, while its diameter, at 135,978 km (84,493 mi), is 0.951 times Jupiter's. Its small size, despite the bloating of the 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.[2]

In addition to heat from its primary star, tidal heating is thought to have played a significant role in this planet's evolution.[7]


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.[8][9] For Winn this is +1 ± 13 degrees.[10]

It has been suggested that there is a second outer planet perturbing HAT-P-2 b, although thus far, this has neither been proven or disproven.[2]


  1. ^ a b Bakos, G. Á.; et al. (2007). "HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star". The Astrophysical Journal. 670 (1): 826–832. arXiv:0705.0126. Bibcode:2007ApJ...670..826B. doi:10.1086/521866.
  2. ^ a b c d Aguilar, David A.; Pulliam, Christine (2007-05-01). "Astronomers find super-massive planet" (Press release). Harvard-Smithsonian Center for Astrophysics. Retrieved 2019-01-05.
  3. ^ a b Bonomo, A. S.; et al. (2017). "The GAPS Programme with HARPS-N at TNG . XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy and Astrophysics. 602 (107): A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.
  4. ^ a b Pál, András; et al. (2010). "Refined stellar, orbital and planetary parameters of the eccentric HAT-P-2 planetary system". Monthly Notices of the Royal Astronomical Society. 401 (4): 2665–2674. arXiv:0908.1705. Bibcode:2010MNRAS.401.2665P. doi:10.1111/j.1365-2966.2009.15849.x.
  5. ^ a b c d Lewis, Nikole K.; et al. (2013). "Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b". The Astrophysical Journal. 766 (2): 95. arXiv:1302.5084. Bibcode:2013ApJ...766...95L. doi:10.1088/0004-637X/766/2/95.
  6. ^ Ravilious, Kate (May 3, 2007). ""Weird" New Planet Weighs as Much as 2,500 Earths". National Geographic News. Retrieved 2007-05-04.
  7. ^ Jackson, Brian; et al. (2008). "Tidal Heating of Extra-Solar Planets". Astrophysical Journal. 681 (2): 1631. arXiv:0803.0026. Bibcode:2008ApJ...681.1631J. doi:10.1086/587641.
  8. ^ Joshua N. Winn (2008). "Measuring accurate transit parameters". Proceedings of the International Astronomical Union. 4: 99–109. arXiv:0807.4929. doi:10.1017/S174392130802629X.
  9. ^ Loeillet, B.; et al. (2008). "Refined parameters and spectroscopic transit of the super-massive planet HD 147506b". Astronomy and Astrophysics. 481 (2): 529–533. arXiv:0707.0679. Bibcode:2008A&A...481..529L. doi:10.1051/0004-6361:20078167.
  10. ^ Winn; et al. (2007). "Spin-Orbit Alignment for the Eccentric Exoplanet HD 147506b". Astrophysical Journal Letters. 665 (2): L167. arXiv:0707.0503. Bibcode:2007ApJ...665L.167W. doi:10.1086/521362.

External links[edit]

Media related to HAT-P-2b at Wikimedia Commons

Coordinates: Sky map 16h 20m 36s, +41° 02′ 53″