Exoplanet · mini-Neptune
HR 858 b
HR 858 b is a mini-Neptune orbiting the star HR 858. Its year lasts 3.59 Earth days. It was discovered in 2019 by the Transit method.
| Host star | HR 858 |
|---|---|
| Distance | 104.3 light-years (32.0 pc) |
| Orbital period | 3.59 days |
| Orbital radius | 0.0489 AU |
| Eccentricity | 0.000 |
| Radius | 2 R⊕ · 0.179 R♃ |
| Mass | 3.55 M⊕ · 0.0112 M♃ |
| Density | 2.44 g/cm³ |
| Surface gravity | 0.884 × Earth |
| Equilibrium temperature | 1,552 K (1,279 °C) |
| Stellar flux received | 990 × Earth |
| Discovery method | Transit |
| Discovery year | 2019 |
| Discovered by | Transiting Exoplanet Survey Satellite (TESS) |
Habitable zone
Inside the inner edge of the habitable zone: it receives 990 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 14° across: 26 times the Sun as we see it from Earth.
In the sky
Visible to the naked eye under a dark sky (apparent magnitude 6.38). Visible from the whole Southern Hemisphere and north to latitude 59° N. South of latitude 59° S it never sets. It stands highest at midnight in November, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1922. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 1.8 million years.
Planets in the same system
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.