The K2-21 System
K2-21 is a planetary system in the constellation Aquarius hosting 2 confirmed exoplanets, about 273 light-years from Earth.
Size Comparison: The Planets of K2-21
K2-21: Star and Habitable Zone
K2-21
- Surface temperature
- 4,222 K (Sun: 5,772 K)
- Mass
- 0.68 M☉
- Radius
- 0.65 R☉
Habitable zone of K2-21: 0.279–0.697 AU (conservative: 0.353–0.661 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
All 2 Planets in the K2-21 System
Discovery History
The first planet found here, K2-21 b, was discovered in 2015 using the transit method.
Frequently Asked Questions About K2-21
How many planets does K2-21 have?
K2-21 has 2 confirmed exoplanets. More may await discovery.
Are any planets in the K2-21 system habitable?
None of the known planets in K2-21 orbit within the star's habitable zone.
How far away is K2-21?
K2-21 is about 273 light-years from Earth in the constellation Aquarius.
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