HD 5278 c
HD 5278 c is a Neptune-like planet orbiting the F V star HD 5278 in the constellation Octans. It lies about 188 light-years from Earth and was discovered in 2021 using the radial velocity method.
Is HD 5278 c in the Habitable Zone?
HD 5278 c orbits inside the inner edge of the habitable zone of HD 5278. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 5278: 1.010–2.356 AU (conservative: 1.279–2.234 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 HD 5278 c — one full orbit around HD 5278 — lasts 40.9 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.242 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.07).
How Was HD 5278 c Discovered?
HD 5278 c was discovered in 2021 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 HD 5278 c?
HD 5278 c is 187.8 light-years (57.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1839. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,305,280 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. HD 5278 c scores 0.20, ranking #3,904 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 5278
HD 5278
- Spectral type
- F V
- Surface temperature
- 6,203 K (Sun: 5,772 K)
- Mass
- 1.13 M☉
- Radius
- 1.19 R☉
- Luminosity
- 1.9070 L☉
- Age
- 3.0 billion years (Sun: 4.6)
The HD 5278 Planetary System
HD 5278 c is one of 2 known planets in the HD 5278 system. Its siblings:
- HD 5278 b (Mini Neptune)
HD 5278 c — Complete Data
| Mass (best estimate) | 18.40 Earth masses |
|---|---|
| Orbital period | 40.87 days |
| Orbital distance | 0.242 AU |
| Eccentricity | 0.070 |
| Earth Similarity Index | 0.20 |
| Distance from Earth | 187.8 light-years (57.6 parsecs) |
| Constellation | Octans |
| Discovery method | Radial Velocity |
| Discovery facility | Paranal Observatory |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-04-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 5278 c
Is HD 5278 c habitable?
No — HD 5278 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 5278 c?
HD 5278 c is about 188 light-years from Earth in the constellation Octans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,305,280 years to get there.
How long is a year on HD 5278 c?
One orbit around HD 5278 takes 40.9 Earth days.
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