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Extrasolar planet List of extrasolar planets
Exoplanet Comparison HAT-P-11 b.png
Size comparison of HAT-P-11b (gray) with Neptune.
Parent star
Star HAT-P-11
Constellation Cygnus
Right ascension (α) 19h 50m 50.25s[1]
Declination (δ) +48° 04′ 51.1″[1]
Apparent magnitude (mV) 9.59[2]
Distance 122 ± 4[1] ly
(37 ± 1[1] pc)
Spectral type K4[2]
Orbital elements
Semimajor axis (a) 0.053+0.0002
Periastron (q) 0.043 AU
Apastron (Q) 0.063 AU
Eccentricity (e) 0.198 ± 0.046
Orbital period (P) 4.8878045±0.0000043[3] d
(0.013381878 ± 0.000000019 y)
Orbital speed (υ) 118 km/s
Inclination (i) 88.5 ± 0.6°
Argument of
(ω) 355.2 ± 17.3°
Time of transit (Tt) 2454605.89132 ± 0.00032 JD
Physical characteristics
Mass (m) 0.081 ± 0.009 MJ
(26 ± 3 M)
Radius (r) 0.422 ± 0.014 RJ
(4.58 ± 0.15 R)
Density (ρ) 1440 kg m-3
Surface gravity (g) 1.20 g
Discovery information
Discovery date January 2, 2009
Discoverer(s) Bakos et al.
Discovery method Transit (HATNet)
Other detection methods Radial velocity
Discovery site Cambridge, Massachusetts
Discovery status Published
Database references
Extrasolar Planets

HAT-P-11b (or Kepler-3b) is an extrasolar planet orbiting the star HAT-P-11. This planet was discovered by the transit method and submitted for publication on January 2, 2009.

This planet is located approximately 122 light-years (37 pc) away[1] in the constellation of Cygnus, orbiting the 10th magnitude K-type star HAT-P-11. This planet was the smallest transiting planet known when first discovered, with a radius about 5 times that of Earth; but is more massive than Gliese 436 b at a true mass of 26 times that of Earth. This planet orbits about the same distance from the star as 51 Pegasi b is from 51 Pegasi, typical of transiting planets. However, the orbit of this planet is eccentric, at around 0.198, unusually high for hot Neptunes. HAT-P-11b's orbit is also highly inclined, with a tilt of approximately 103 degrees relative to its star's rotation.[4][5]

The HAT-P-11 system was within the field of view of the Kepler spacecraft.[2]

Its radial velocity is drifting and this may be a result of an as-yet-undiscovered planet in the system.[2]

The planet fits models for 90% heavy elements. Expected temperature is 878 ± 15K.[2] Actual temperature must await calculations of secondary transit.

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b c d e Bakos, G. Á. et al. (2010). "HAT-P-11b: A Super-Neptune Planet Transiting a Bright K Star in the Kepler Field". The Astrophysical Journal 710 (2): 1724–1745. arXiv:0901.0282. Bibcode:2010ApJ...710.1724B. doi:10.1088/0004-637X/710/2/1724. 
  3. ^ Dittmann, Jason A.; Close, Laird M.; Green, Elizabeth M.; Scuderi, Louis J.; Males, Jared R. (2009). "Follow-up Observations of the Neptune Mass Transiting Extrasolar Planet HAT-P-11b". The Astrophysical Journal 699: L48–L51. arXiv:0905.1114v2. Bibcode:2009ApJ...699L..48D. doi:10.1088/0004-637X/699/1/L48. 
  4. ^ "Inclined Orbits Prevail in Exoplanetary Systems". January 12, 2011. 
  5. ^ Roberto Sanchis-Ojeda, Josh N. Winn, Daniel C. Fabrycky (2012). Starspots and spin-orbit alignment for Kepler cool host stars. arXiv:1211.2002. Bibcode:2013AN....334..180S. doi:10.1002/asna.201211765. 

External links[edit]

Media related to HAT-P-11b at Wikimedia Commons

Coordinates: Sky map 19h 50m 50.2469s, +48° 04′ 51.085″