| Observation data Epoch J2000 Equinox J2000  | |
|---|---|
| Constellation | Cygnus | 
| Right ascension | 20h 02m 27.376s [2] | 
| Declination | +30° 04′ 25.49″ [2] | 
| Apparent magnitude (V) | 8.6-9.6 [1] | 
| Characteristics | |
| Evolutionary stage | Yellow supergiant [3] | 
| Spectral type | G7Ia [3] | 
| U−B color index | +1.9 –+2.8 [1] | 
| B−V color index | +2.1 –+2.5 [1] | 
| Variable type | L [4] | 
| Astrometry | |
| Proper motion (μ) | RA: −2.936 [2]  mas/yr  Dec.: −5.55 [2] mas/yr  | 
| Parallax (π) | 0.2390±0.0178 mas [2] | 
| Distance | 14,000 ± 1,000  ly  (4,200 ± 300 pc)  | 
| Absolute magnitude (MV) | −7.956 [3] | 
| Details | |
| Mass | 10.3 [5] M☉ | 
| Radius | 559 [3] [a] R☉ | 
| Luminosity | 176,200 [3] L☉ | 
| Surface gravity (log g) | −0.81 [6] cgs | 
| Temperature | 5,000 [3] K | 
| Metallicity [Fe/H] | −0.42 [5] dex | 
| Other designations | |
| HD 333385, TYC 2670-4475-1, 2MASS J20022738+3004252 | |
| Database references | |
| SIMBAD | data | 
V1027 Cygni is a luminous yellow supergiant star located in the constellation of Cygnus, about 14,000 light years away. For a time, it was thought that it could be a low-mass post-AGB star, however recent parallax measurements published in Gaia DR3 have shown this to likely not be the case, and instead it is likely a massive yellow supergiant star. [3]
V1027 Cygni has a surface temperature about 5,000 K, which has been found in many studies. However, studies before Gaia DR3 generally used a distance around 1,280 pc , which led to low luminosity estimates, hence a tentative post-AGB star status. [1] Recent Gaia DR3 data shows that V1027 Cygni is likely much further away, over 4,000 pc away, which implies a much higher luminosity (about 176,000 L☉) which would place it firmly outside the post-AGB star luminosity range and in that of the more massive, younger yellow supergiants. [3] Spectral indicators of luminosity also suggest a supergiant status. [1]
Assuming a temperature of 5,000 K and a luminosity of about 176,200 L☉ for V1027 Cygni leads to a size of about 560 times that of the Sun. [a]
When V1027 Cygni was first noticed as a variable star, it was thought to be an irregular variable, dimming and brightening erratically with no discernible period. However, in 2009, a small-amplitude period of 237 days was observed in long-term photometry of the star. [1]