Extrasolar planet List of extrasolar planets
Size comparison of HAT-P-2b with Jupiter.
Parent star

<tr> <td colspan="2">Star</td> <td>HD 147506</td></tr><tr> <td colspan="2">Constellation</td> <td>Hercules[1]</td></tr><tr> <td>Right ascension</td> <td style="text-align: center">(α)</td> <td>16h 20m 36.36s[2]</td></tr><tr> <td>Declination</td> <td style="text-align: center">(δ)</td> <td>+41° 02′ 53.1″[2]</td></tr><tr><td colspan="2">Distance</td><td>370 ± 30[2] ly
(114 ± 10[2] pc)</td></tr><tr><td colspan="2">Spectral type</td> <td>F8V[3]</td></tr>

Orbital elements

<tr><td>Semimajor axis</td><td style="text-align: center">(a)</td> <td>0.0663 ± 0.0039[4] AU</td></tr><tr> <td>Eccentricity</td> <td style="text-align: center">(e)</td> <td>0.50910 ± 0.00048[4]</td></tr><tr><td>Orbital period</td><td style="text-align: center">(P)</td> <td>5.6334729 ± 0.0000061 days[5] d</td></tr><tr> <td>Inclination</td> <td style="text-align: center">(i)</td> <td>85.97 +0.28
[4]°</td></tr><tr> <td>Argument of
</td> <td style="text-align: center">(ω)</td> <td>188.09 ± 0.39[4]°</td></tr><tr> <td>Time of periastron</td> <td style="text-align: center">(T0)</td> <td>2,455,289.4721 ± 0.0038[4] JD</td></tr><tr> <td>Semi-amplitude</td> <td style="text-align: center">(K)</td> <td>983.9 ± 17.2[5] m/s</td></tr>

Physical characteristics

<tr><td>Mass</td><td style="text-align: center">(m)</td><td>8.00 ± 0.97[4] MJ</td></tr><tr><td>Radius</td><td style="text-align: center">(r)</td><td>1.106 ± 0.061[4] Template:Jupiter radius</td></tr><tr><td>Density</td><td style="text-align: center">(ρ)</td><td>7,300 ± 1,600[4] kg m-3</td></tr><tr><td>Surface gravity</td><td style="text-align: center">(g)</td><td>162 ± 27[4] m/s²</td></tr><tr> <td>Temperature</td> <td style="text-align: center">(T)</td> <td>1187[6] K</td></tr>

Discovery information

<tr> <td colspan="2">Discovery date</td> <td>2007-05-02</td></tr><tr> <td colspan="2">Discoverer(s)</td> <td>HATNet Project[3]</td></tr><tr> <td colspan="2">Discovery method</td> <td>Transit</td></tr><tr> <td colspan="2">Other detection methods</td> <td>Radial velocity,
Orbital phase reflected light variations</td></tr><tr> <td colspan="2">Discovery status</td> <td>Published[3]</td></tr>

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 370 light-years away in the constellation Hercules. Every 5 days 15 hours, it crosses directly in front of the star as viewed from Earth.[7][3]

Orbit and massEdit

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.[7]

In addition to heat from its primary star, tidal heating is thought to have played a significant role in this planet's evolution.[8]


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.[9][10] For Winn this is +1 ± 13 degrees.[11]

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.[7]


  1. (1987). Identification of a Constellation From a Position. Publications of the Astronomical Society of the Pacific 99 (617): 695–699.Vizier query form
  2. 2.0 2.1 2.2 2.3 (2007). Validation of the new Hipparcos reduction. Astronomy and Astrophysics 474 (2): 653–664.Vizier catalog entry
  3. 3.0 3.1 3.2 3.3 (2007). HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star. The Astrophysical Journal 670 (1): 826–832.
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 (2013). Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b. The Astrophysical Journal 766 (2).
  5. 5.0 5.1 (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.
  6. Template:Cite news
  7. 7.0 7.1 7.2 Script error
  8. Jackson, Brian (2008). Tidal Heating of Extra-Solar Planets. ApJ 681 (2): 1631.
  9. Joshua N. Winn (2008). Measuring accurate transit parameters. Proceedings of the International Astronomical Union 4: 99.
  10. (2008). Refined parameters and spectroscopic transit of the super-massive planet HD 147506b. Astronomy and Astrophysics 481 (2).
  11. Winn et al. (2007). . Astrophysical Journal (Letters) 665.

External linksEdit


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

Ad blocker interference detected!

Wikia is a free-to-use site that makes money from advertising. We have a modified experience for viewers using ad blockers

Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.