Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cepheus |
Right ascension | 22h 23m 07.01521s[1] |
Declination | +55° 57′ 47.6244″[1] |
Apparent magnitude (V) | +6.65[2] (6.0–7.6[3]) |
Characteristics | |
Evolutionary stage | Red, orange or yellow hypergiant |
Spectral type | K2 0-Ia[4] (G8 - M2Ia-0[3]) |
Apparent magnitude (K) | 1.88[2] |
U−B color index | 2.38[2] |
B−V color index | 2.22[2] |
Variable type | SRd[5] |
Astrometry | |
Radial velocity (Rv) | −56.00[6] km/s |
Proper motion (μ) | RA: −3.606[1] mas/yr Dec.: −2.881[1] mas/yr |
Parallax (π) | 0.1140 ± 0.0342 mas[1] |
Distance | 3,400+220 −200 pc[7][8] |
Absolute magnitude (MV) | −8.0[9] – −9.4[10] |
Details | |
Mass | 25 – 40 (initial mass)[11] M☉ |
Radius | 1,100±44[11] R☉ |
Luminosity | 300,000[8] – 540,000[11] L☉ |
Surface gravity (log g) | 0.2[12] cgs |
Temperature | 4,200[13]–4,400,[8] 3,900[13] (during the dimming) K |
Metallicity [Fe/H] | +0.17±0.20[14] dex |
Other designations | |
Database references | |
SIMBAD | data |
RW Cephei is a K-type hypergiant and a semirregular variable star in the constellation Cepheus, at the edge of the Sharpless 132 H II region and close to the small open cluster Berkeley 94. It is among the largest stars known with a radius of 1,100 times that of the Sun (R☉), nearly as large as the orbit of Jupiter.
In 2022, the star underwent a "great dimming" event similar to Betelgeuse.
The temperature intermediate between the red supergiants and yellow hypergiants has led to it being variously considered as a red hypergiant[15][16] or yellow hypergiant.[17][18]
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