Exoplanet · mini-Neptune
HD 39855 b
HD 39855 b is a mini-Neptune orbiting the star HD 39855. Its year lasts 3.25 Earth days. It was discovered in 2019 by the Radial Velocity method.
| Host star | HD 39855 |
|---|---|
| Distance | 75.9 light-years (23.3 pc) |
| Orbital period | 3.25 days |
| Orbital radius | 0.041 AU |
| Eccentricity | 0.140 |
| Radius | 2.85 R⊕ · 0.254 R♃ |
| Mass (minimum) | 8.5 M⊕ · 0.0267 M♃ |
| Density | 2.02 g/cm³ |
| Equilibrium temperature | 1,146 K (873 °C) |
| Stellar flux received | 287 × Earth |
| Discovery method | Radial Velocity |
| Discovery year | 2019 |
| Discovered by | Las Campanas Observatory |
Habitable zone
Inside the inner edge of the habitable zone: it receives 287 times the light the Earth does, too hot to keep liquid water on its surface.
Its star in the sky
In the planet's sky its star is a disc 9.7° across: 18 times the Sun as we see it from Earth.
In the sky
Too faint for the naked eye (magnitude 7.51); binoculars will find it. Visible from the whole Southern Hemisphere and north to latitude 70° N. South of latitude 70° S it never sets. It stands highest at midnight in December, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1950. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 1.3 million years.
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.