HD 101581 c
HD 101581 c is a terrestrial planet orbiting HIP 56998 in the constellation Centaurus. It lies about 42 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is HD 101581 c?
HD 101581 c has a radius of 0.99 times that of Earth.
Is HD 101581 c in the Habitable Zone?
HD 101581 c orbits inside the inner edge of the habitable zone of HIP 56998. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HIP 56998: 0.328–0.803 AU (conservative: 0.415–0.761 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 101581 c
The equilibrium temperature of HD 101581 c is about 747 K (474 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 52.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 101581 c — one full orbit around HIP 56998 — lasts 6.20 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.057 AU — closer to its star than Mercury is to the Sun.
How Was HD 101581 c Discovered?
HD 101581 c was discovered in 2025 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 HD 101581 c?
HD 101581 c is 41.7 light-years (12.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1985. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 733,920 years to make the journey.
The Host Star: HIP 56998
HIP 56998
- Surface temperature
- 4,675 K (Sun: 5,772 K)
- Mass
- 0.65 M☉
- Radius
- 0.63 R☉
- Age
- 6.9 billion years (Sun: 4.6)
The HIP 56998 Planetary System
HD 101581 c is one of 2 known planets in the HIP 56998 system. Its siblings:
- HD 101581 b (Terrestrial)
HD 101581 c — Complete Data
| Radius | 0.990 Earth radii (0.088 Jupiter radii) |
|---|---|
| Orbital period | 6.20 days |
| Orbital distance | 0.057 AU |
| Equilibrium temperature | 747 K (474 °C) |
| Stellar irradiation | 52.00× Earth |
| Distance from Earth | 41.7 light-years (12.8 parsecs) |
| Constellation | Centaurus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-01-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 101581 c
Is HD 101581 c habitable?
No — HD 101581 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 101581 c?
HD 101581 c is about 42 light-years from Earth in the constellation Centaurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 733,920 years to get there.
How big is HD 101581 c compared to Earth?
HD 101581 c has 0.99 times the radius of Earth.
How long is a year on HD 101581 c?
One orbit around HIP 56998 takes 6.2 Earth days — short enough that 59 of its years would fit into one Earth year.
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