  | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Musca |
| Right ascension | 12h 12m 47.01834s |
| Declination | −70° 09′ 06.4363″ |
| Apparent magnitude (V) | 5.89 - 6.49 |
| Characteristics | |
| Spectral type | F6Ib (F6-G0) + B5V |
| U−B color index | +0.66 |
| B−V color index | +1.00 |
| Variable type | δ Cepheid |
| Astrometry | |
| Radial velocity (Rv) | −1.91 km/s |
| Proper motion (μ) | RA: −7.79 mas/yr Dec.: −0.60 mas/yr |
| Parallax (π) | 1.99±0.84 mas |
| Distance | 2,798 ± 55 ly (858±17 pc) |
| Absolute magnitude (MV) | −4.01 |
| Orbit | |
| Period (P) | 506.3±0.5 days |
| Semi-major axis (a) | (2.95±0.09)×10−3" (2.53±0.09 AU) |
| Eccentricity (e) | 0.088±0.006 |
| Inclination (i) | 144.7±2.8° |
| Longitude of the node (Ω) | 99.6±14.4° |
| Periastron epoch (T) | 2,457,165.9±4.4 JD |
| Argument of periastron (ω) (secondary) | 194.8±3.3° |
| Semi-amplitude (K1) (primary) | 14.85±0.03 km/s |
| Semi-amplitude (K2) (secondary) | 16.63±3.27 km/s |
| Details | |
| S Mus A | |
| Mass | 4.44±0.91 M☉ |
| Radius | 65.1 R☉ |
| Luminosity | 3,467 L☉ |
| Metallicity | +0.18 |
| S Mus B | |
| Mass | 3.98±0.21 M☉ |
| Temperature | 17,000 K |
| Other designations | |
| S Mus, HR 4645, SAO 251791, CD−69°977, GSC 09231-00752, HD 106111, GC 16679, HIP 59551, AAVSO 1207-69 | |
| Database references | |
| SIMBAD | data |
S Muscae is a classical (δ) Cepheid variable star in the constellation Musca about 2,800 light years away.
S Muscae is a yellow supergiant ranging between spectral types F6Ib and G0Ib and magnitudes 5.89 to 6.49 over a period of 9.66 days. It is a luminous star around six times as massive as the Sun and 65.1 times the radius of the Sun. It is a binary star with a blue-white main sequence star companion likely to be of spectral type B3V to B5V with a mass of just over five solar masses, one of the hottest and brightest companions of a Cepheid known. The two stars orbit each other every 505 days.
S Muscae has been found to lie within the faint star cluster ASCC 69.
