HD 40307 g
The parameters of this planet are disputed or ambiguous in the scientific literature.
HD 40307 g is a super-Earth orbiting the K2.5 V star HD 40307 in the constellation Pictor. It lies about 42 light-years from Earth and was discovered in 2013 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 HD 40307 g in the Habitable Zone?
HD 40307 g orbits inside the conservative habitable zone of HD 40307 — 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 HD 40307: 0.376–0.911 AU (conservative: 0.476–0.864 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 40307 g — one full orbit around HD 40307 — lasts 197.8 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.600 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.29).
How Was HD 40307 g Discovered?
HD 40307 g was discovered in 2013 using the radial velocity method, with observations from La Silla 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 40307 g?
HD 40307 g is 42.2 light-years (12.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1984. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 742,720 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 40307 g scores 0.66, ranking #84 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 40307
HD 40307
- Spectral type
- K2.5 V
- Surface temperature
- 4,956 K (Sun: 5,772 K)
- Mass
- 0.77 M☉
- Luminosity
- 0.2296 L☉
- Age
- 4.5 billion years (Sun: 4.6)
The HD 40307 Planetary System
HD 40307 g is one of 5 known planets in the HD 40307 system. Its siblings:
- HD 40307 b (Super Earth)
- HD 40307 c (Super Earth)
- HD 40307 d (Super Earth)
- HD 40307 f (Super Earth)
HD 40307 g — Complete Data
| Mass (best estimate) | 7.10 Earth masses |
|---|---|
| Orbital period | 197.80 days |
| Orbital distance | 0.600 AU |
| Eccentricity | 0.290 |
| Earth Similarity Index | 0.66 |
| Distance from Earth | 42.2 light-years (12.9 parsecs) |
| Constellation | Pictor |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 40307 g
Is HD 40307 g habitable?
HD 40307 g orbits within the habitable zone of HD 40307, 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 HD 40307 g?
HD 40307 g is about 42 light-years from Earth in the constellation Pictor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 742,720 years to get there.
How long is a year on HD 40307 g?
One orbit around HD 40307 takes 197.8 Earth days.
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