Exoplanet · Neptune-like planet
TOI-257 b
TOI-257 b is a Neptune-like planet orbiting the star TOI-257. Its year lasts 18.4 Earth days. It was discovered in 2021 by the Transit method.
| Host star | TOI-257 |
|---|---|
| Distance | 250.8 light-years (76.9 pc) |
| Orbital period | 18.4 days |
| Orbital radius | 0.153 AU |
| Eccentricity | 0.000 |
| Radius | 7.16 R⊕ · 0.639 R♃ |
| Mass | 43.9 M⊕ · 0.138 M♃ |
| Density | 0.65 g/cm³ |
| Surface gravity | 0.855 × Earth |
| Equilibrium temperature | 1,027 K (754 °C) |
| Stellar flux received | 186 × Earth |
| Discovery method | Transit |
| Discovery year | 2021 |
| Discovered by | Transiting Exoplanet Survey Satellite (TESS) |
Habitable zone
Inside the inner edge of the habitable zone: it receives 186 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 6.5° across: 12 times the Sun as we see it from Earth.
In the sky
Too faint for the naked eye (magnitude 7.57); binoculars will find it. Visible from the whole Southern Hemisphere and north to latitude 39° N. South of latitude 39° 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 1775. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 4.4 million years.
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.