Star · M0.0
K2-21
K2-21 is a main-sequence star of spectral type M0.0 in the constellation Aquarius, 272.6 light-years from the Sun. It is orbited by 2 confirmed exoplanet(s).
| Constellation | Aquarius |
|---|---|
| Distance | 272.6 light-years (83.6 pc) |
| Apparent magnitude | magnitude 12.82 |
| Absolute magnitude | magnitude 8.21 |
| Spectral type | M0.0 |
| Surface temperature | 4,220 K |
| Luminosity | 0.104 L☉ |
| Radius | 0.647 R☉ |
| Mass | 0.676 M☉ |
| Age | 1.0 billion years |
| Metallicity [Fe/H] | -0.11 |
| Right ascension (J2000) | 22h 41m 12.9s |
| Declination (J2000) | −14° 29′ 22″ |
| Space velocity (relative to the Sun) | 32.7 km/s |
In the sky
A telescope is needed to see it: its apparent magnitude is 12.82. Visible from the whole Southern Hemisphere and north to latitude 76° N. South of latitude 76° S it never sets. It stands highest at midnight in August, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out around the year 1753. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 4.8 million years.
The Sun seen from there
From a planet around K2-21, the Sun would look like a star of magnitude 9.44, in the direction where our sky has the constellation Leo. It would be invisible to the naked eye.
Planets
Neighbours
Its nearest neighbours in the catalogue (within 20 light-years):
- HIP 111892 17.3 light-years
- HIP 112959 19.3 light-years
- HIP 113117 19.4 light-years
Stellar parameters from the NASA Exoplanet Archive; position and brightness from the HYG / AT-HYG catalogue.