Rho Cephei, a white main-sequence star in Cepheus
Rho Cephei is a white main-sequence star in the constellation Cepheus. At 240 light years away, it shines at an apparent visual magnitude of 5.46.
Rho Cephei (HIP 111056)
Rho Cephei is a white main-sequence star in the constellation Cepheus. At 240 light years away, it shines at an apparent visual magnitude of 5.46. It is moving through the Galaxy at a speed of 7.5 km/s relative to the Sun.
Sky position: RA 22h 29.9m, Dec +78° 49.5'
Common designations: Rho Cephei, Rho-2 Cephei, 29 Cephei, HR 8591, HD 213798, Gaia DR3 2285649898351302656, HIP 111056
Rho Cephei has the spectral type A3V. A-type stars are white stars with surface temperatures of roughly 7,500 to 10,000 K. Their spectra are dominated by strong hydrogen lines, and many of them rotate rapidly. Its luminosity class V means it is a main-sequence (dwarf) star, still fusing hydrogen into helium in its core like the Sun.
How to find Rho Cephei in the sky
Rho Cephei lies in Cepheus. With a declination of +78° 49.5', it is visible from the entire Northern Hemisphere and from the Southern Hemisphere down to about latitude 11° S. Observers poleward of latitude 11° 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 Rho Cephei
Astrometry and spectroscopy
| Right Ascension (J2000) | 337.47074152° (22h 29.9m) |
| Declination (J2000) | 78.82428668° (+78° 49.5') |
| Galactic Longitude | 116.15937786° |
| Galactic Latitude | 17.86113791° |
| Proper motion RA | 3.54 mas/yr |
| Proper motion Dec | -20.84 mas/yr |
| Parallax | 13.60 ± 0.05 mas |
| Spectral Type | A3V |
| Radial Velocity | -1.25 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 5.62 | 1.29 |
| B | 5.54 | 1.21 |
| V | 5.46 | 1.13 |
| J | 5.26 | 0.92 |
| H | 5.29 | 0.96 |
| K | 5.23 | 0.90 |
Colour index B-V: +0.08
Derivations
- Heliocentric distance: 73.51 pc (240 light years) (0.4% margin of error)
- Absolute visual magnitude: 1.13
- Transverse velocity: 7.4 km/s
- Space velocity relative to the Sun: 7.5 km/s
- Galactic position (X, Y, Z): -30.8 pc, 62.8 pc, 22.5 pc
- Galactic velocity (U, V, W): 2.2 km/s, 2.1 km/s, -6.8 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.