The K2-138 System
K2-138 is a planetary system in the constellation Aquarius hosting 6 confirmed exoplanets, about 661 light-years from Earth.
Size Comparison: The Planets of K2-138
K2-138: Star and Habitable Zone
K2-138
- Surface temperature
- 5,356 K (Sun: 5,772 K)
- Mass
- 0.94 M☉
- Radius
- 0.86 R☉
- Age
- 2.8 billion years (Sun: 4.6)
Habitable zone of K2-138: 0.570–1.361 AU (conservative: 0.722–1.290 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 6 Planets in the K2-138 System
Discovery History
The first planet found here, K2-138 b, was discovered in 2017 using the transit method. The most recent addition, K2-138 g, followed in 2021.
Frequently Asked Questions About K2-138
How many planets does K2-138 have?
K2-138 has 6 confirmed exoplanets. More may await discovery.
Are any planets in the K2-138 system habitable?
None of the known planets in K2-138 orbit within the star's habitable zone.
How far away is K2-138?
K2-138 is about 661 light-years from Earth in the constellation Aquarius.
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