HAT-P-11b (orKepler-3b) is an extrasolar planet orbiting the star HAT-P-11. It was discovered by the HATNet Project team in 2009 using the transit method, and submitted for publication on 2 January 2009.
Size comparison of Neptune with HAT-P-11b (gray).
| |
| Discovery[1] | |
|---|---|
| Discovered by | Bakos et al. |
| Discovery site | Cambridge, Massachusetts |
| Discovery date | 2 January 2009 |
| Transit (HATNet) | |
| Orbital characteristics | |
| Apastron | 0.0637+0.0020 −0.0019 AU |
| Periastron | 0.0413+0.0018 −0.0019 AU |
| 0.05254+0.00064 −0.00066 AU | |
| Eccentricity | 0.218+0.034 −0.031[2] |
| 4.887802443+0.000000034 −0.000000030[3] d | |
| Inclination | 89.05+0.15 −0.09[3] |
| 2454957.15+0.17 −0.20[2] | |
| 19+14 −16[2] | |
| Semi-amplitude | 10.42+0.64 −0.66[2] |
| Star | HAT-P-11 |
| Physical characteristics | |
| 4.36±0.06[3] R🜨 | |
| Mass | 23.4±1.5[2] ME |
Mean density | 1.44 g/cm3 |
| 1.20 g | |
This planet is located approximately 123 light-years (38 pc) distant from Earth.[4]
The HATNet Project team initially detected the transits of HAT-P-11b from analysis of 11470 images, taken in 2004 and 2005, by the HAT-6 and HAT-9 telescopes. The planet was confirmed using 50 radial velocity measurements taken with the HIRES radial velocity spectrometer at W. M. Keck Observatory.[1]
At the time of its discovery HAT-P-11b was the smallest radius transiting extrasolar planet discovered by a ground based transit search and was also one of three previously known transiting planets within the initial field of view of the Kepler spacecraft.[1]
There was a linear trend in the radial velocities indicating the possibility of another planet in the system.[1] This planet, HAT-P-11c, was confirmed in 2018.[2]
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 103+26
−10°.[5] degrees relative to its star's rotation.[6][7] The planet is probably composed primarily of heavy elements with only 10% hydrogen and helium by mass, like Gliese 436 b.[1]
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.[8]
In 2009 French astronomers observed what was thought to be a weak unpolarized radio signal coming from the exoplanet, but it was not observed in a repeat observation in 2010.[9] If the signal was real, then it was probably due to intense lightning storms with similar properties as ones on Saturn.[10]
In December 2021 evidence of a magnetosphere was discovered in HAT-P-11b that could be the first ever in any exoplanet.[11][12][13]
Media related to HAT-P-11b at Wikimedia Commons