The Kepler-21 system contains 1 exoplanet. It is located 353.95 light years away from the solar system.
| Mass | 1.41 solar masses |
| Radius | 1.9 solar radiae |
| Temperature | 6305 kelvin |
| Stellar Metallicity | -0.03 decimal exponent |
| Age | 3.03 billion years |
At more than 10 Earth masses, Kepler-21 b is an ice giant, a planet that is made up mostly of volatiles like water, amonia and methane, and enveloped by a dense hydrogen and helium atmosphere, much like Uranus and Neptune.
| Mass | 5.080 Earth masses |
| Density | 6.400 grams per cubic centimeter |
| Radius | 1.639 Earth radiae |
| Semi-major Axis | 0.042717 AU |
| Eccentricity | 0.02 |
| Orbital Period | 2.786 days |
| Discovery Method | Transit |
| Discovery Facility | Kepler |
| Discovery Telescope | 0.95 m Kepler Telescope |
| Discovery Instrument | Kepler CCD Array |
| Discovery Date | 2012-02 |
| Reference | Howell et al. 2012 |