HD 81817 is 878 light-years from the Sun. The NASA Exoplanet Archive lists 2 planets around this K3 III star; the first was found in 2020 by radial velocity (Bohyunsan Optical Astronomical Observatory).
Fly there in 3DHD 81817 b takes 2.8 years to go round its star once.
| Spectral type | K3 III |
| Surface temperature | 4,140 K |
| Mass | 4.3 solar masses |
| Radius | 83.8 solar radii |
| Luminosity | 1823 times the Sun |
| Apparent magnitude | 4.26489 |
| Age | about 0.15 billion years |
| Distance from the Sun | 877.8 light-years (269.1 parsecs) |
| Position (J2000) | RA 144.2716°, Dec 81.3263° |
| Constellation | Draco |
| Planet | Year | Orbit | Radius | Mass | Found |
|---|---|---|---|---|---|
| HD 81817 c | 623.0 days | 2.325 AU | 12 R⊕ estimated | 7185.8 M⊕ minimum | Radial Velocity, 2022 |
| HD 81817 b | 2.8 years | 3.233 AU | 12 R⊕ estimated | 7668.6 M⊕ | Radial Velocity, 2020 |
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 4,140 K, 1,823 times as bright as the Sun, the habitable zone, where starlight could keep water liquid on a rocky surface, runs from about 43.72 to 82.26 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 878 years ago, around 1150.