Star · A2
21 Her
21 Her is a main-sequence star of spectral type A2 in the constellation Hercules, 351.5 light-years from the Sun.
| Other names | HIP 80351 |
|---|---|
| Constellation | Hercules |
| Distance | 351.5 light-years (107.8 pc) |
| Apparent magnitude | magnitude 5.83 |
| Absolute magnitude | magnitude 0.67 |
| Spectral type | A2 |
| Surface temperature | 9,910 K |
| Luminosity | 62.8 L☉ |
| Radius | 2.69 R☉ |
| Mass | 2.96 M☉ (estimated) |
| Right ascension (J2000) | 16h 24m 10.8s |
| Declination (J2000) | +6° 56′ 54″ |
| Space velocity (relative to the Sun) | 41.7 km/s |
In the sky
Visible to the naked eye under a dark sky (apparent magnitude 5.83). Visible from the whole Northern Hemisphere and south to latitude 83° S. It stands highest at midnight in May, the best time to observe it.
Through a telescope from Earth
Light's journey
The light you see tonight set out around the year 1674. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 6.2 million years.
The Sun seen from there
From a planet around 21 Her, the Sun would look like a star of magnitude 9.99, in the direction where our sky has the constellation Eridanus. It would be invisible to the naked eye.
Position, brightness and colour from the HYG / AT-HYG catalogue; temperature, luminosity, radius and mass are approximate values computed from these observations.