Exoplanet · super-Earth
Kepler-21 b
Kepler-21 b is a super-Earth orbiting the star Kepler-21. Its year lasts 2.79 Earth days. It was discovered in 2012 by the Transit method.
| Host star | Kepler-21 |
|---|---|
| Distance | 354.0 light-years (108.5 pc) |
| Orbital period | 2.79 days |
| Orbital radius | 0.0434 AU |
| Eccentricity | 0.000 |
| Radius | 1.64 R⊕ · 0.146 R♃ |
| Mass | 7.5 M⊕ · 0.0236 M♃ |
| Density | 9.3 g/cm³ |
| Surface gravity | 2.79 × Earth |
| Equilibrium temperature | 2,015 K (1,742 °C) |
| Stellar flux received | 2,750 × Earth |
| Discovery method | Transit |
| Discovery year | 2012 |
| Discovered by | Kepler |
Habitable zone
Inside the inner edge of the habitable zone: it receives 2,750 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 23° across: 43 times the Sun as we see it from Earth.
In the sky
Too faint for the naked eye (magnitude 8.25); binoculars will find it. Visible from the whole Northern Hemisphere and south to latitude 51° S. North of latitude 51° N it never sets. It stands highest at midnight in July, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1672. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 6.3 million years.
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.