K2-157 d
K2-157 d is a Neptune-like planet orbiting the G9 V star K2-157 in the constellation Virgo. It lies about 973 light-years from Earth and was discovered in 2025 using the radial velocity method.
Is K2-157 d in the Habitable Zone?
K2-157 d orbits inside the inner edge of the habitable zone of K2-157. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of K2-157: 0.564–1.348 AU (conservative: 0.715–1.278 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on K2-157 d
The equilibrium temperature of K2-157 d is about 429 K (156 °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 6.46 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on K2-157 d — one full orbit around K2-157 — lasts 66.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.309 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.50), swinging dramatically closer to and farther from its star.
How Was K2-157 d Discovered?
K2-157 d was discovered in 2025 using the radial velocity method, with observations from Paranal Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is K2-157 d?
K2-157 d is 973.2 light-years (298.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1053. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 17,128,320 years to make the journey.
The Host Star: K2-157
K2-157
- Spectral type
- G9 V
- Surface temperature
- 5,334 K (Sun: 5,772 K)
- Mass
- 0.89 M☉
- Radius
- 0.86 R☉
- Age
- 8.8 billion years (Sun: 4.6)
The K2-157 Planetary System
K2-157 d is one of 3 known planets in the K2-157 system. Its siblings:
K2-157 d — Complete Data
| Mass (best estimate) | 23.30 Earth masses |
|---|---|
| Orbital period | 66.50 days |
| Orbital distance | 0.309 AU |
| Eccentricity | 0.500 |
| Equilibrium temperature | 429 K (156 °C) |
| Stellar irradiation | 6.46× Earth |
| Distance from Earth | 973.2 light-years (298.4 parsecs) |
| Constellation | Virgo |
| Discovery method | Radial Velocity |
| Discovery facility | Paranal Observatory |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-05-13. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About K2-157 d
Is K2-157 d habitable?
No — K2-157 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is K2-157 d?
K2-157 d is about 973 light-years from Earth in the constellation Virgo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 17,128,320 years to get there.
How long is a year on K2-157 d?
One orbit around K2-157 takes 66.5 Earth days.
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