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HAT-P-7b / Kepler-2b
Exoplanet Comparison HAT-P-7 b.png
Size comparison of HAT-P-7b (gray) with Jupiter.
Discovered byHATNet Project
Discovery dateMarch 6, 2008
Orbital characteristics
0.03813±0.00036 AU
2.204737±0.000017[3] d
Physical characteristics
Mean radius
Mass1.806±0.036[2] MJ
Mean density
g cm−3
24.75 m/s2 (81.2 ft/s2)
2.524 g

HAT-P-7b (or Kepler-2b) is an extrasolar planet discovered in 2008. It orbits very close to its host star, and is both larger and more massive than Jupiter. Due to the extreme heat it receives from its star, the dayside temperature is predicted to be 2730+150
K. HAT-P-7b is also one of the darkest planets ever observed, with an albedo of less than 0.03—meaning it absorbs more than 97% of the visible light that strikes it.[4]


The GSC 03547-01402 system was within the initial field of view of the Kepler Mission spacecraft,[1] which confirmed the transit and orbital properties of the planet with significantly improved confidence and observed occultation and light curve characteristics consistent with a strongly absorbing atmosphere with limited advection to the night side. In testing itself on HAT-P-7b, Kepler proved it was sensitive enough to detect Earth-like exoplanets.[5]

In August 2009, it was announced that HAT-P-7b may have a retrograde orbit, based upon measurements of the Rossiter–McLaughlin effect.[6][7][8] This announcement came only a day after the announcement of the first planet discovered with such an orbit, WASP-17b.

In January 2010, it was announced that ellipsoidal light variations were detected for HAT-P-7b, the first detection of such kind. This method analyses the brightness variation caused by the rotation of a star as its shape tidally distorted by the planet.[9]

On July 4, 2011, HAT-P-7b was the subject of the Hubble Space Telescope's one millionth scientific observation.[10]


In December 2016, a letter published in Nature Astronomy by Dr. David Armstrong and his colleagues described evidence of strong wind jets of variable speed on HAT-P-7b.[11] High variation in wind speed would explain similar variations in light reflected from HAT-P-7b's atmosphere. In particular, the brightest point on the planet shifts its phase or position on a timescale of only tens to hundreds of days, suggesting high variation in global wind speeds and cloud coverage. Condensation models of HAT-P-7b predict precipitation of Al2O3 (corundum) on the night side of the planet's atmosphere. Because corundum gems are rubies and sapphires, one can describe the hypothetical weather on the planet's night side as "raining rubies and sapphires."[11][12]

See also[edit]


  1. ^ a b Pál, A.; et al. (2008). "HAT-P-7b: An Extremely Hot Massive Planet Transiting a Bright Star in the Kepler Field". The Astrophysical Journal. 680 (2): 1450–1456. arXiv:0803.0746. Bibcode:2008ApJ...680.1450P. doi:10.1086/588010.
  2. ^ 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. A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.
  3. ^ Morris, Brett M.; et al. (2013). "Kepler's Optical Secondary Eclipse of HAT-P-7b and Probable Detection of Planet-induced Stellar Gravity Darkening". The Astrophysical Journal Letters. 764 (2). L22. arXiv:1301.4503. Bibcode:2013ApJ...764L..22M. doi:10.1088/2041-8205/764/2/L22.
  4. ^ WASP-104b is Darker Than Charcoal
  5. ^ Borucki, W. J.; et al. (2009-08-07). "Kepler's Optical Phase Curve of the Exoplanet HAT-P-7b". Science. 325 (5941): 709. Bibcode:2009Sci...325..709B. doi:10.1126/science.1178312. PMID 19661420.
  6. ^ Second backwards planet found, a day after the first
  7. ^ HAT-P-7: A Retrograde or Polar Orbit, and a Second Planet
  8. ^ First Evidence of a Retrograde Orbit of Transiting Exoplanet HAT-P-7b
  9. ^ The Discovery of Ellipsoidal Variations in the Kepler Light Curve of HAT-P-7: William F. Welsh, Jerome A. Orosz, Sara Seager, Jonathan J. Fortney, Jon Jenkins, Jason F. Rowe, David Koch, William J. Borucki
  10. ^ NASA'S Hubble Makes One Millionth Science Observation
  11. ^ a b Armstrong, D.J., de Mooij, E., Barstow, J., Osborn, H.P., Blake, J. and Saniee, N.F., 2016. Variability in the atmosphere of the hot giant planet HAT-P-7 b. arXiv preprint arXiv:1612.04225.
  12. ^ Pat Brennan (December 11, 2016). "Winds of rubies and sapphires strike the sky of giant planet". Exoplanets.nasa.gov. NASA. Retrieved May 22, 2019.

External links[edit]

Coordinates: Sky map 19h 28m 59s, +47° 58′ 10″