Kepler-549 d
Kepler-549 d is a Neptune-like planet orbiting Kepler-549 in the constellation Lyra. It lies about 2,072 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-549 d?
Kepler-549 d has a radius of 4.20 times that of Earth.
Is Kepler-549 d in the Habitable Zone?
Kepler-549 d orbits inside the inner edge of the habitable zone of Kepler-549. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-549: 0.556–1.326 AU (conservative: 0.704–1.257 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-549 d
The equilibrium temperature of Kepler-549 d is about 586 K (313 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 27.93 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-549 d — one full orbit around Kepler-549 — lasts 24.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.158 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-549 d Discovered?
Kepler-549 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-549 d?
Kepler-549 d is 2,071.6 light-years (635.1 parsecs) from Earth. Light arriving here tonight left the planet about 2,072 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 36,460,160 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-549 d scores 0.23, ranking #3,558 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-549
Kepler-549
- Surface temperature
- 5,360 K (Sun: 5,772 K)
- Mass
- 0.88 M☉
- Radius
- 0.84 R☉
- Age
- 4.6 billion years (Sun: 4.6)
The Kepler-549 Planetary System
Kepler-549 d is one of 3 known planets in the Kepler-549 system. Its siblings:
- Kepler-549 b (Mini Neptune)
- Kepler-549 c (Mini Neptune)
Kepler-549 d — Complete Data
| Radius | 4.200 Earth radii (0.375 Jupiter radii) |
|---|---|
| Orbital period | 24.61 days |
| Orbital distance | 0.158 AU |
| Equilibrium temperature | 586 K (313 °C) |
| Stellar irradiation | 27.93× Earth |
| Earth Similarity Index | 0.23 |
| Distance from Earth | 2,071.6 light-years (635.1 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-549 d
Is Kepler-549 d habitable?
No — Kepler-549 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-549 d?
Kepler-549 d is about 2,072 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 36,460,160 years to get there.
How big is Kepler-549 d compared to Earth?
Kepler-549 d has 4.20 times the radius of Earth.
How long is a year on Kepler-549 d?
One orbit around Kepler-549 takes 24.6 Earth days — short enough that 15 of its years would fit into one Earth year.
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