HAT-P-11 b
HAT-P-11 b is a Neptune-like planet orbiting HAT-P-11 in the constellation Cygnus. It lies about 123 light-years from Earth and was discovered in 2008 using the transit method.
Is HAT-P-11 b in the Habitable Zone?
The position of HAT-P-11 b relative to the habitable zone of HAT-P-11 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HAT-P-11 b — one full orbit around HAT-P-11 — lasts 4.89 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.053 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.25).
How Was HAT-P-11 b Discovered?
HAT-P-11 b was discovered in 2008 using the transit method, with observations from HATNet.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is HAT-P-11 b?
HAT-P-11 b is 123.2 light-years (37.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1903. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,168,320 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. HAT-P-11 b scores 0.18, ranking #4,053 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HAT-P-11
HAT-P-11
- Mass
- 0.81 M☉
The HAT-P-11 Planetary System
HAT-P-11 b is one of 2 known planets in the HAT-P-11 system. Its siblings:
- HAT-P-11 c (Cold Gas Giant)
HAT-P-11 b — Complete Data
| Mass (best estimate) | 23.52 Earth masses |
|---|---|
| Orbital period | 4.89 days |
| Orbital distance | 0.053 AU |
| Eccentricity | 0.251 |
| Earth Similarity Index | 0.18 |
| Distance from Earth | 123.2 light-years (37.8 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | HATNet |
| Discovery year | 2008 |
Data: NASA Exoplanet Archive, last updated 2025-02-24. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HAT-P-11 b
Is HAT-P-11 b habitable?
HAT-P-11 b is not known to orbit within the habitable zone of HAT-P-11, and as a Neptune-like planet it is an unlikely candidate for life as we know it.
How far away is HAT-P-11 b?
HAT-P-11 b is about 123 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,168,320 years to get there.
How long is a year on HAT-P-11 b?
One orbit around HAT-P-11 takes 4.9 Earth days — short enough that 75 of its years would fit into one Earth year.
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