NML Cygni
NML Cygni or V1489 Cygni (abbreviated to NML Cyg or V1489 Cyg) is a red hypergiant or red supergiant (RSG) in the constellation Cygnus. It is possibly one of the largest known stars currently known by radius, and is also possibly one of the most luminous and massive cool hypergiants, as well as one of the most luminous stars in the Milky Way.
NML Cygni, seen as the deep red star at the center, from the Sloan Digital Sky Survey DR9. Note the green circumstellar nebula surrounding the star. | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 46m 25.54s |
| Declination | +40° 06′ 59.4″ |
| Apparent magnitude (V) | 16.60 (variable) |
| Characteristics | |
| Evolutionary stage | OH/IR red hypergiant |
| Spectral type | M4.5–M7.9 Ia–III |
| Apparent magnitude (K) | 12.3 |
| Apparent magnitude (B) | 18.64 |
| Apparent magnitude (V) | 16.60 |
| Apparent magnitude (G) | 11.0330 |
| Apparent magnitude (J) | 4.877 |
| Apparent magnitude (H) | 2.389 |
| B−V color index | +2.04 |
| Variable type | SRc |
| Astrometry | |
| Proper motion (μ) | RA: −1.55 mas/yr Dec.: −4.59 mas/yr |
| Parallax (π) | 0.620 ± 0.047 mas |
| Distance | 5,250+420 −360 ly (1,610+130 −110 pc) |
| Details | |
| Mass | 40 M☉ |
| Luminosity | 229,000+40,000 −41,000 L☉ |
| Temperature | 3,300 K |
| Age | 8 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The distance of NML Cygni from Earth is estimated to be around 1.6 kpc, about 5,300 light-years. It is a part of the Cygnus OB2 association, one of the closest massive associations to the Sun, spanning nearly 2° on the sky or ~30 pc in radius at the distance of 1.74±0.2 kpc.
The radius of NML Cyg is uncertain but it was given calculations between 1,183 and 2,770 times that of the Sun (R☉). If placed at the center of the Solar System, its surface would potentially extend past the orbit of Jupiter or Saturn.