HD 154391 b
HD 154391 b is a cold gas giant orbiting the K1 III star HD 154391 in the constellation Draco. It lies about 329 light-years from Earth and was discovered in 2023 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 154391 b in the Habitable Zone?
HD 154391 b orbits inside the conservative habitable zone of HD 154391 — 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 154391: 4.857–11.785 AU (conservative: 6.152–11.174 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 154391 b — one full orbit around HD 154391 — lasts 5,163.0 Earth days, longer than Jupiter's 12-year orbit. It orbits at an average distance of 7.460 AU. Its orbit is mildly elliptical (eccentricity 0.20).
How Was HD 154391 b Discovered?
HD 154391 b was discovered in 2023 using the radial velocity method, with observations from Multiple Observatories.
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 154391 b?
HD 154391 b is 329.2 light-years (100.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1697. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,793,920 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 154391 b scores 0.38, ranking #547 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 154391
HD 154391
- Spectral type
- K1 III
- Surface temperature
- 4,909 K (Sun: 5,772 K)
- Mass
- 2.07 M☉
- Radius
- 8.56 R☉
- Luminosity
- 38.1197 L☉
- Age
- 1.1 billion years (Sun: 4.6)
Planetary System
HD 154391 b is the only planet known to orbit HD 154391 so far.
HD 154391 b — Complete Data
| Mass | 2,892.24 Earth masses (9.100 Jupiter masses) |
|---|---|
| Orbital period | 5,163.00 days |
| Orbital distance | 7.460 AU |
| Eccentricity | 0.200 |
| Earth Similarity Index | 0.38 |
| Distance from Earth | 329.2 light-years (100.9 parsecs) |
| Constellation | Draco |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-12-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 154391 b
Is HD 154391 b habitable?
HD 154391 b orbits within the habitable zone of HD 154391, 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 154391 b?
HD 154391 b is about 329 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,793,920 years to get there.
How long is a year on HD 154391 b?
One orbit around HD 154391 takes 5,163.0 Earth days.
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