55 Cnc B c
55 Cnc B c is a super-Earth orbiting the M4.5 V star 55 Cnc B in the constellation Cancer. It lies about 41 light-years from Earth and was discovered in 2025 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is 55 Cnc B c in the Habitable Zone?
55 Cnc B c orbits inside the conservative habitable zone of 55 Cnc B — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of 55 Cnc B: 0.073–0.191 AU (conservative: 0.092–0.181 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on 55 Cnc B c — one full orbit around 55 Cnc B — lasts 33.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.130 AU — closer to its star than Mercury is to the Sun.
How Was 55 Cnc B c Discovered?
55 Cnc B c was discovered in 2025 using the radial velocity method, with observations from Mauna Kea 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 55 Cnc B c?
55 Cnc B c is 40.7 light-years (12.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1986. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 716,320 years to make the journey.
The Host Star: 55 Cnc B
55 Cnc B c belongs to a system of 2 stars; it orbits 55 Cnc B.
55 Cnc B
- Spectral type
- M4.5 V
- Surface temperature
- 3,286 K (Sun: 5,772 K)
- Mass
- 0.26 M☉
- Radius
- 0.27 R☉
- Age
- 10.0 billion years (Sun: 4.6)
The 55 Cnc B Planetary System
55 Cnc B c is one of 2 known planets in the 55 Cnc B system. Its siblings:
- 55 Cnc B b (Super Earth)
55 Cnc B c — Complete Data
| Mass (best estimate) | 5.30 Earth masses |
|---|---|
| Orbital period | 33.75 days |
| Orbital distance | 0.130 AU |
| Distance from Earth | 40.7 light-years (12.5 parsecs) |
| Constellation | Cancer |
| Discovery method | Radial Velocity |
| Discovery facility | Mauna Kea Observatory |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-10-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About 55 Cnc B c
Is 55 Cnc B c habitable?
55 Cnc B c orbits within the habitable zone of 55 Cnc B, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is 55 Cnc B c?
55 Cnc B c is about 41 light-years from Earth in the constellation Cancer. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 716,320 years to get there.
How long is a year on 55 Cnc B c?
One orbit around 55 Cnc B takes 33.7 Earth days — short enough that 11 of its years would fit into one Earth year.
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