Herschel's Garnet Star, a red supergiant star in Cepheus
Herschel's Garnet Star is a red supergiant star in the constellation Cepheus. At 27,408 light years away, it shines at an apparent visual magnitude of 4.08.
Herschel's Garnet Star (HIP 107259)
Herschel's Garnet Star is a red supergiant star in the constellation Cepheus. At 27,408 light years away, it shines at an apparent visual magnitude of 4.08. It is moving through the Galaxy at a speed of 214.7 km/s relative to the Sun.
Sky position: RA 21h 43.5m, Dec +58° 46.8'
Common designations: Herschel's Garnet Star, Erakis, Mu Cephei, HR 8316, HD 206936, Gaia DR3 2202630001603369856, HIP 107259
Herschel's Garnet Star has the spectral type M2-Ia. M-type stars are cool red stars below about 3,900 K whose spectra are dominated by titanium oxide molecular bands. Red dwarfs, red giants and red supergiants all fall in this class. Its luminosity class I marks it as a supergiant, among the most luminous and largest stars known.
How to find Herschel's Garnet Star in the sky
Herschel's Garnet Star lies in Cepheus. With a declination of +58° 46.8', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 31° S. Observers poleward of latitude 31° N see it as circumpolar: it never sets. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around September, which makes the weeks around that month the best time to observe it.
Tabulated data for Herschel's Garnet Star
Astrometry and spectroscopy
| Right Ascension (J2000) | 325.87691482° (21h 43.5m) |
| Declination (J2000) | 58.78004609° (+58° 46.8') |
| Galactic Longitude | 100.59524068° |
| Galactic Latitude | 4.31498103° |
| Proper motion RA | 3.44 mas/yr |
| Proper motion Dec | -4.11 mas/yr |
| Parallax | 0.12 ± 0.26 mas |
| Spectral Type | M2-Ia |
| Radial Velocity | 23.00 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 8.85 | -5.77 |
| B | 6.43 | -8.19 |
| V | 4.08 | -10.54 |
| R | 1.98 | -12.64 |
| I | 0.22 | -14.40 |
| J | -0.52 | -15.14 |
| H | -1.27 | -15.89 |
| K | -1.72 | -16.34 |
Colour index B-V: +2.35
Derivations
- Heliocentric distance: 8,403.36 pc (27,408 light years) (221.6% margin of error)
- Absolute visual magnitude: -10.54
- Transverse velocity: 213.4 km/s
- Space velocity relative to the Sun: 214.7 km/s
- Galactic position (X, Y, Z): -1540.7 pc, 8236.7 pc, 632.3 pc
- Galactic velocity (U, V, W): -4.2 km/s, 38.9 km/s, -211.1 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.