| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 21h 25m 16.95755s[1] |
| Declination | −03° 33′ 24.2964″[1] |
| Apparent magnitude (V) | 5.48[2] |
| Characteristics | |
| Spectral type | K4III[3] |
| B−V color index | 1.451±0.011[2] |
| Astrometry | |
| Radial velocity (Rv) | −24.5±2[4] km/s |
| Proper motion (μ) | RA: −12.061[1] mas/yr Dec.: −69.973[1] mas/yr |
| Parallax (π) | 7.8747 ± 0.2182 mas[1] |
| Distance | 410 ± 10 ly (127 ± 4 pc) |
| Absolute magnitude (MV) | 0.11[2] |
| Details | |
| Radius | 28.01+1.09 −2.12[1] R☉ |
| Luminosity | 203.4±6.4[1] L☉ |
| Surface gravity (log g) | 1.79[5] cgs |
| Temperature | 4119+165 −78[1] K |
| Metallicity [Fe/H] | −0.08[5] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
21 Aquarii is a single[6] star in the zodiac constellation of Aquarius. 21 Aquarii is the Flamsteed designation. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.49.[2] This object is a member of the HR 1614 moving group,[7] and is moving closer to the Earth with a heliocentric radial velocity of −24.5 km/s.[4]
This object is an evolved giant star with a stellar classification of K4 III.[3] As a result of having exhausted the hydrogen at its core, it has expanded to 27[1] times the radius of the Sun. The star is radiating 203[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,120 K.[1]
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