Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cassiopeia |
Right ascension | 02h 32m 42.537s [1] |
Declination | 61° 27′ 21.57″ [1] |
Apparent magnitude (V) | 7.87 [2] |
Characteristics | |
Spectral type | O4.5III(f) [3] (O5.5III(f) + O7V [4]) |
U−B color index | −0.55 [2] |
B−V color index | +0.43 [2] |
V−R color index | +0.38 [2] |
R−I color index | +0.40 [2] |
J−H color index | +0.18 [2] |
Astrometry | |
Radial velocity (Rv) | −45.10±1.50 [5] km/s |
Proper motion (μ) |
RA: −0.478
[1]
mas/
yr Dec.: −0.849 [1] mas/ yr |
Parallax (π) | 0.5764 ± 0.0662 mas [1] |
Distance | approx. 5,700
ly (approx. 1,700 pc) |
Orbit | |
Period (P) | 442 days
[4] (1.2 [4] yr) |
Semi-major axis (a) | 726 R☉ [4] |
Eccentricity (e) | 0.37±0.07 [4] |
Argument of periastron (ω) (secondary) | 120 [4]° |
Details | |
Mass | >152±51 [4] M☉ |
Radius | 16.4 [6] R☉ |
Luminosity | ~660,000 [4] L☉ |
Surface gravity (log g) | 3.7 [6] cgs |
Temperature | 39,500 [6] K |
Age | 0.7-3 [4] [7] Myr |
secondary | |
Mass | 46±11 [4] M☉ |
Radius | 5.6 [6] R☉ |
Other designations | |
Database references | |
SIMBAD | data |
HD 15558 (HIP 11832) is a massive O-type multiple star system in Cassiopeia and is specifically in our galaxy's Heart Nebula in the open cluster IC 1805. The primary is a very massive star with 152 M☉ and 660,000 L☉.
HD 15558 A is a spectroscopic binary system containing at least two massive luminous class O stars. The primary is an O4.5 giant star with a surface temperature over 46,800 K. It has a mass of 152 M☉ and a luminosity of 660,000 L☉, making it one of the most massive stars in the Milky Way Galaxy. The star loses 1.5×10−5 M☉ per year. [7] The secondary is an O7V star. It has a mass of 46 M☉. The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters. [4]
The Washington Double Star Catalog lists 11 companions within one arc minute of HD 15558 A, all fainter than 10th magnitude. In addition, it lists component E just over one arc minute away; it is another hot massive star, the 9th magnitude BD+60°501 with a spectral type of O7 V(n)((f))z. [3] [8]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cassiopeia |
Right ascension | 02h 32m 42.537s [1] |
Declination | 61° 27′ 21.57″ [1] |
Apparent magnitude (V) | 7.87 [2] |
Characteristics | |
Spectral type | O4.5III(f) [3] (O5.5III(f) + O7V [4]) |
U−B color index | −0.55 [2] |
B−V color index | +0.43 [2] |
V−R color index | +0.38 [2] |
R−I color index | +0.40 [2] |
J−H color index | +0.18 [2] |
Astrometry | |
Radial velocity (Rv) | −45.10±1.50 [5] km/s |
Proper motion (μ) |
RA: −0.478
[1]
mas/
yr Dec.: −0.849 [1] mas/ yr |
Parallax (π) | 0.5764 ± 0.0662 mas [1] |
Distance | approx. 5,700
ly (approx. 1,700 pc) |
Orbit | |
Period (P) | 442 days
[4] (1.2 [4] yr) |
Semi-major axis (a) | 726 R☉ [4] |
Eccentricity (e) | 0.37±0.07 [4] |
Argument of periastron (ω) (secondary) | 120 [4]° |
Details | |
Mass | >152±51 [4] M☉ |
Radius | 16.4 [6] R☉ |
Luminosity | ~660,000 [4] L☉ |
Surface gravity (log g) | 3.7 [6] cgs |
Temperature | 39,500 [6] K |
Age | 0.7-3 [4] [7] Myr |
secondary | |
Mass | 46±11 [4] M☉ |
Radius | 5.6 [6] R☉ |
Other designations | |
Database references | |
SIMBAD | data |
HD 15558 (HIP 11832) is a massive O-type multiple star system in Cassiopeia and is specifically in our galaxy's Heart Nebula in the open cluster IC 1805. The primary is a very massive star with 152 M☉ and 660,000 L☉.
HD 15558 A is a spectroscopic binary system containing at least two massive luminous class O stars. The primary is an O4.5 giant star with a surface temperature over 46,800 K. It has a mass of 152 M☉ and a luminosity of 660,000 L☉, making it one of the most massive stars in the Milky Way Galaxy. The star loses 1.5×10−5 M☉ per year. [7] The secondary is an O7V star. It has a mass of 46 M☉. The primary may itself be a double star, suggested by the improbably large mass found from the binary orbit when compared to the other stellar parameters. [4]
The Washington Double Star Catalog lists 11 companions within one arc minute of HD 15558 A, all fainter than 10th magnitude. In addition, it lists component E just over one arc minute away; it is another hot massive star, the 9th magnitude BD+60°501 with a spectral type of O7 V(n)((f))z. [3] [8]