21 Sagittarii, an orange giant star in Sagittarius
21 Sagittarii is an orange giant star in the constellation Sagittarius. At 481 light years away, it shines at an apparent visual magnitude of 4.86.
21 Sagittarii (HIP 90289)
21 Sagittarii is an orange giant star in the constellation Sagittarius. At 481 light years away, it shines at an apparent visual magnitude of 4.86. It is moving through the Galaxy at a speed of 22.0 km/s relative to the Sun.
Sky position: RA 18h 25.4m, Dec -20° 32.5'
Common designations: 21 Sagittarii, HR 6896, HD 169420, HD 169421, HIP 90289, Gaia DR3 4091210409716888704
21 Sagittarii has the spectral type K1/2III. K-type stars are orange stars with surface temperatures of about 3,900 to 5,300 K. Their spectra are rich in neutral metal lines and, in the cooler examples, molecular bands. Its luminosity class III marks it as a giant: an evolved star that has left the main sequence and swollen to many times its original size.
How to find 21 Sagittarii in the sky
21 Sagittarii lies in Sagittarius. With a declination of -20° 32.5', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 69° N. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around July, which makes the weeks around that month the best time to observe it.
Tabulated data for 21 Sagittarii
Astrometry and spectroscopy
| Right Ascension (J2000) | 276.33766429° (18h 25.4m) |
| Declination (J2000) | -20.54167284° (-20° 32.5') |
| Galactic Longitude | 11.73604380° |
| Galactic Latitude | -3.74641431° |
| Proper motion RA | 6.11 mas/yr |
| Proper motion Dec | -26.70 mas/yr |
| Parallax | 6.78 ± 0.22 mas |
| Spectral Type | K1/2III |
| Radial Velocity | -10.75 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| B | 6.32 | 0.48 |
| V | 4.86 | -0.98 |
| J | 2.22 | -3.63 |
| H | 1.55 | -4.29 |
| K | 1.42 | -4.43 |
Colour index B-V: +1.46
Derivations
- Heliocentric distance: 147.42 pc (481 light years) (3.3% margin of error)
- Absolute visual magnitude: -0.98
- Transverse velocity: 19.1 km/s
- Space velocity relative to the Sun: 22.0 km/s
- Galactic position (X, Y, Z): 144.0 pc, 29.9 pc, -9.6 pc
- Galactic velocity (U, V, W): -8.3 km/s, -16.6 km/s, -11.7 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.