|Exoplanet||List of exoplanets|
|Right ascension||(α)||19h 50m 50.2469s|
|Declination||(δ)||+48° 04′ 51.101″|
|Eccentricity||(e)||0.198 ± 0.046|
|Orbital period||(P)||4.8878045±0.0000043 d|
(0.013381878 ± 0.000000019 y)
|Orbital speed||(υ)||118 km/s|
|Inclination||(i)||88.5 ± 0.6°|
|(ω)||355.2 ± 17.3°|
|Time of transit||(Tt)||2454605.89132 ± 0.00032 JD|
|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 date||2 January 2009|
|Discoverer(s)||Bakos et al.|
|Discovery method||Transit (HATNet)|
|Other detection methods||Radial velocity|
|Discovery site||Cambridge, Massachusetts|
|Open Exoplanet Catalogue||data|
This planet is located approximately 124 light-years (38 pc) away in the constellation of Cygnus, orbiting the 10th apparent 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.
Its radial velocity is drifting and this may be a result of an as-yet-undiscovered planet in the system.
On 24 September 2014, NASA reported that HAT-P-11b is the first Neptune-sized exoplanet known to have a relatively cloud-free atmosphere and, as well, the first time molecules, namely water vapor, of any kind have been found on such a relatively small exoplanet. In 2009 French astronomers observed what was thought to be a weak radio signal coming from the exoplanet. In 2016 scientists from the University of St Andrews set out to solve the mystery. They assumed that the signal was real and was coming from the planet and investigated whether it can be produced by lightning on HAT-P-11b. Assuming that the underlying physics of lightning is the same for all Solar System planets, like Earth and Saturn, as well as on HAT-P-11b, the researchers found that 3.8 × 10^6 lightning flashes of Saturnian lightning-strength in a square kilometre per hour would explain the observed radio signal on HAT-P-11b. This storm would have been so enormous that the largest thunder storms on Earth or Saturn would have produced <1% of the strength of the signal coming from the planet.
- Brown, A. G. A; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics. 595. A2. arXiv: . Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512.Gaia Data Release 1 catalog entry
- 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: . Bibcode:2010ApJ...710.1724B. doi:10.1088/0004-637X/710/2/1724.
- 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: . Bibcode:2009ApJ...699L..48D. doi:10.1088/0004-637X/699/1/L48.
- "Inclined Orbits Prevail in Exoplanetary Systems". 12 January 2011.
- Roberto Sanchis-Ojeda; Josh N. Winn; Daniel C. Fabrycky (2012). "Starspots and spin-orbit alignment for Kepler cool host stars". Astronomische Nachrichten. 334: 180–183. arXiv: . Bibcode:2013AN....334..180S. doi:10.1002/asna.201211765.
- Clavin, Whitney; Chou, Felicia; Weaver, Donna; Villard; Johnson, Michele (24 September 2014). "NASA Telescopes Find Clear Skies and Water Vapor on Exoplanet". NASA. Retrieved 24 September 2014.
- "Could ferocious lightning storms beam radio signals to Earth?". 26 April 2016.
- "Lightning as a possible source of the radio emission on HAT-P-11b". ADS. arXiv: . Bibcode:2016MNRAS.461.1222H. doi:10.1093/mnras/stw977.
Media related to HAT-P-11b at Wikimedia Commons
- "HAT-P-11 b". Exoplanets.