The star
The star
HD 39091
- Type
- G0 V
- Surface
- ≈ 5,998 K
- Size
- 1.19 × the Sun
- Mass
- 1.07 × the Sun
- Brightness
- 1.44 × the Sun
- Habitable zone
- 0.89–2.09 AU
The planets
HD 39091
pi Men c
- Year
- 6.27 days
- Distance from star
- 0.0684 AU
- Mass
- 3.6 Earths
- Size
- 2 × Earth
- Temperature
- ≈ 1170 K (+897 °C)
- Found
- 2018, transit (Transiting Exoplanet Survey Satellite (TESS))
HD 39091
pi Men d
- Year
- 124.64 days
- Distance from star
- 0.506 AU
- Mass
- at least 13 Earths
- Size
- 3.7 × Earth
- Temperature
- ≈ 444 K (+170 °C)
- Found
- 2022, radial velocity (La Silla Observatory)
HD 39091
HD 39091 b
- Year
- 5.7 years
- Distance from star
- 3.28 AU
- Mass
- 14 Jupiters
- Size
- 12 × Earth
- Temperature
- ≈ 173 K (-100 °C)
- Found
- 2001, radial velocity (Anglo-Australian Telescope)
Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.
How we know
The wobble
The planet tugs its star back and forth. Spectrographs measure the tiny shift in the star's light, which gives the planet's year and a minimum mass.
The shadow
The planet passes in front of its star and dims it by a fraction of a percent, every orbit. The dip gives the planet's size and year.
Sources
- Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 31 Oct 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
- Position: HYG Database v4.1 (CC BY-SA 4.0).
- Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.