K2-138 is 661 light-years from the Sun. The NASA Exoplanet Archive lists 6 planets around this G8 V star; the first was found in 2017 by transit (K2).
Fly there in 3DK2-138 b goes round its star every 2.35 days, 37 times as often as Mercury goes round the Sun.
| Spectral type | G8 V |
| Surface temperature | 5,356 K |
| Mass | 0.935 solar masses |
| Radius | 0.863 solar radii |
| Luminosity | 0.517 times the Sun |
| Apparent magnitude | 12.246 |
| Age | about 2.8 billion years |
| Distance from the Sun | 660.7 light-years (202.6 parsecs) |
| Position (J2000) | RA 348.9490°, Dec -10.8497° |
| Constellation | Aquarius |
| Planet | Year | Orbit | Radius | Mass | Found |
|---|---|---|---|---|---|
| K2-138 b | 2.35 days | 0.0338 AU | 1.51 R⊕ | 3.1 M⊕ | Transit, 2017 |
| K2-138 c | 3.56 days | 0.0446 AU | 2.299 R⊕ | 6.31 M⊕ | Transit, 2017 |
| K2-138 d | 5.40 days | 0.0589 AU | 2.39 R⊕ | 7.92 M⊕ | Transit, 2017 |
| K2-138 e | 8.26 days | 0.0782 AU | 3.39 R⊕ | 12.97 M⊕ | Transit, 2017 |
| K2-138 f | 12.8 days | 0.104 AU | 2.904 R⊕ | 1.63 M⊕ | Transit, 2017 |
| K2-138 g | 42.0 days | 0.231 AU | 3.013 R⊕ | 4.32 M⊕ | Transit, 2021 |
Values are the NASA Exoplanet Archive’s composite parameters. A radius marked estimated comes from a mass–radius relation; a mass marked minimum is M sin i. Planet sizes and colours in the 3D view are renderings: none of these worlds has been photographed as more than a point of light.
For a star of 5,356 K, 0.52 times as bright as the Sun, the habitable zone, where starlight could keep water liquid on a rocky surface, runs from about 0.70 to 1.25 AU. None of its known planets orbits inside it. The zone says how much starlight arrives, not whether a planet has water or air. The edges follow Kopparapu et al. (2014), as the 3D view draws them.
The light you see left 661 years ago, around 1370.