18 Cephei, a red giant star in Cepheus
18 Cephei is a red giant star in the constellation Cepheus. At 433 light years away, it shines at an apparent visual magnitude of 5.30.
18 Cephei (HIP 108924)
18 Cephei is a red giant star in the constellation Cepheus. At 433 light years away, it shines at an apparent visual magnitude of 5.30. It is moving through the Galaxy at a speed of 43.8 km/s relative to the Sun.
Sky position: RA 22h 3.9m, Dec +63° 7.2'
Common designations: 18 Cephei, MO Cephei, HR 8416, HD 209772, Gaia DR3 2205941009060265728, HIP 108924
18 Cephei has the spectral type M5III. 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 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 18 Cephei in the sky
18 Cephei lies in Cepheus. With a declination of +63° 7.2', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 27° S. Observers poleward of latitude 27° 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 18 Cephei
Astrometry and spectroscopy
| Right Ascension (J2000) | 330.97073768° (22h 3.9m) |
| Declination (J2000) | 63.11992085° (+63° 7.2') |
| Galactic Longitude | 105.25641315° |
| Galactic Latitude | 6.15185552° |
| Proper motion RA | 37.04 mas/yr |
| Proper motion Dec | 58.29 mas/yr |
| Parallax | 7.53 ± 0.12 mas |
| Spectral Type | M5III |
| Radial Velocity | -5.30 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| B | 6.77 | 1.15 |
| V | 5.30 | -0.32 |
| J | 1.28 | -4.34 |
| H | 0.36 | -5.25 |
| K | 0.13 | -5.49 |
Colour index B-V: +1.47
Derivations
- Heliocentric distance: 132.75 pc (433 light years) (1.6% margin of error)
- Absolute visual magnitude: -0.32
- Transverse velocity: 43.5 km/s
- Space velocity relative to the Sun: 43.8 km/s
- Galactic position (X, Y, Z): -34.7 pc, 127.3 pc, 14.2 pc
- Galactic velocity (U, V, W): -37.4 km/s, -17.4 km/s, 14.8 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.