HD 39091 planetary system
HD 39091 is a Sun-like main-sequence star of spectral type G0 V approximately 59.6 light-years from Earth (18.27 parsecs). It hosts 3 confirmed exoplanets. 1 planet transits the host star from our line of sight, allowing direct measurements of size and atmosphere.
Host star
- Name
- HD 39091
- Spectral type
- G0 V
- Effective temperature
- 5,998 K
- Mass
- 1.07 M☉ (solar masses)
- Radius
- 1.17 R☉ (solar radii)
- Distance
- 18.27 pc (59.6 ly)
- Hipparcos catalog
- HIP 26394
Confirmed planets (3)
| Planet | Class | Mass (M⊕) | Radius (R⊕) | Period (d) | Distance (AU) | Eq. temp (K) | Discovered |
|---|---|---|---|---|---|---|---|
| pi Men c | Mini-Neptune | 3.63 | 2.02 | 6.27 | 0.0684 | 1,170 | 2018 |
| pi Men d | Mini-Neptune | 13.38 | 3.72 | 124.64 | 0.5060 | — | 2022 |
| HD 39091 b | Neptune-like | 4481.38 | 12.30 | 2088.80 | 3.2800 | — | 2001 |
The planets in detail
pi Men c is a Mini-Neptune with about 2.02 Earth radii and 3.63 Earth masses. It orbits HD 39091 at 0.0684 AU with a 6.3-day year, soaked in over 309× Earth's stellar flux, and a scorching equilibrium temperature of 1170 K. The planet transits its host star, which is how its radius and (when combined with mass) bulk density are pinned down. It was confirmed in 2018 via the transit method.
pi Men d is a Mini-Neptune with about 3.72 Earth radii and 13.38 Earth masses. It orbits HD 39091 at 0.5060 AU with a 125-day year, and no published equilibrium temperature. Its orbit is notably eccentric (e = 0.22), meaning the distance to its star — and the irradiation it receives — varies substantially over each year. It was confirmed in 2022 via radial velocity (Doppler) measurements.
HD 39091 b is a Neptune-like world with about 12.30 Earth radii and 4481.38 Earth masses. It orbits HD 39091 at 3.2800 AU with a 5.7-Earth-year orbit, and no published equilibrium temperature. Its orbit is notably eccentric (e = 0.64), meaning the distance to its star — and the irradiation it receives — varies substantially over each year. It was confirmed in 2001 via radial velocity (Doppler) measurements.
Discovery
The HD 39091 system was first identified in 2001, with confirmation work continuing through 2022 using radial velocity (Doppler) measurements. Detection facilities: Transiting Exoplanet Survey Satellite (TESS), La Silla Observatory, Anglo-Australian Telescope.
Observing from Earth
Exoplanets cannot be resolved visually with amateur telescopes — the host star's glare is overwhelming and even space-based direct imaging requires sophisticated coronagraphs. What you can observe is the host star itself at right ascension 84.2993°, declination -80.4646°. Because 1 planet transits from our perspective, advanced amateurs with photometric setups can sometimes detect the resulting brightness dips. Use the 3D orrery above to inspect orbital geometry, planetary scale, and the habitable-zone overlay — the orbits are computed from the published Keplerian elements and animate at user-controlled time rates.
