Kepler-311 d
Kepler-311 d is a mini-Neptune orbiting Kepler-311 in the constellation Lyra. It lies about 2,540 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-311 d?
Kepler-311 d has a radius of 2.05 times that of Earth.
Is Kepler-311 d in the Habitable Zone?
Kepler-311 d orbits inside the inner edge of the habitable zone of Kepler-311. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-311: 0.924–2.170 AU (conservative: 1.170–2.057 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-311 d
The equilibrium temperature of Kepler-311 d is about 327 K (54 °C) — in a range broadly comparable to Earth, whose equilibrium temperature is 255 K. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 2.71 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-311 d — one full orbit around Kepler-311 — lasts 232.0 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.733 AU — comparable to the inner Solar System.
How Was Kepler-311 d Discovered?
Kepler-311 d was discovered in 2023 using the transit method, with observations from Kepler.
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 Kepler-311 d?
Kepler-311 d is 2,539.6 light-years (778.7 parsecs) from Earth. Light arriving here tonight left the planet about 2,540 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 44,696,960 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. Kepler-311 d scores 0.58, ranking #157 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-311
Kepler-311
- Surface temperature
- 5,905 K (Sun: 5,772 K)
- Radius
- 1.19 R☉
The Kepler-311 Planetary System
Kepler-311 d is one of 3 known planets in the Kepler-311 system. Its siblings:
- Kepler-311 b (Super Earth)
- Kepler-311 c (Super Earth)
Kepler-311 d — Complete Data
| Radius | 2.050 Earth radii (0.183 Jupiter radii) |
|---|---|
| Orbital period | 232.04 days |
| Orbital distance | 0.733 AU |
| Equilibrium temperature | 327 K (54 °C) |
| Stellar irradiation | 2.71× Earth |
| Earth Similarity Index | 0.58 |
| Distance from Earth | 2,539.6 light-years (778.7 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2017-05-08. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-311 d
Is Kepler-311 d habitable?
No — Kepler-311 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-311 d?
Kepler-311 d is about 2,540 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 44,696,960 years to get there.
How big is Kepler-311 d compared to Earth?
Kepler-311 d has 2.05 times the radius of Earth.
How long is a year on Kepler-311 d?
One orbit around Kepler-311 takes 232.0 Earth days.
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