Trumpler 27-1

The Trumpler 27 open cluster. Trumpler 27-1 is the brightest and reddest star in the image.
Observation data Epoch J2000       Equinox J2000
Constellation	Scorpius
Right ascension	17h 36m 10.1193s [1]
Declination	−33° 29′ 40.617″ [1]
Apparent magnitude (V)	8.79 [2]
Characteristics
Evolutionary stage	Red supergiant
Spectral type	M0Ia [2]
Astrometry
Radial velocity (Rv)	−18.71±0.9 [1] km/s
Proper motion (μ)	RA: −0.057±0.049  mas/ yr [1] Dec.: −1.386±0.037  mas/ yr [1]
Parallax (π)	0.3169 ± 0.0361  mas [1]
Distance	approx. 10,000  ly (approx. 3,200  pc)
Details [3]
Radius	1,359  R☉
Luminosity	361,000  L☉
Surface gravity (log g)	-0.24 [4]  cgs
Temperature	3,790  K
Metallicity [Fe/H]	+0.15 [4]  dex
Other designations
CD−33 12241, CPD−33 4468, TYC 7380-627-1 [2]
Database references
SIMBAD	data

Trumpler 27-1 is a red supergiant star that is a member of the massive, possible open cluster Trumpler-27, where a blue giant star, a yellow supergiant star, and two Wolf–Rayet stars are also located.

Trumpler 27-1 was discovered and catalogued when the open cluster (not confirmed then) was first identified in the late 20th century.^{[ citation needed]} It has since remained largely unobserved, being featured in the Gaia Catalogue and other pieces of literature. ^[5]

Trumpler 27-1 is among the largest stars known, with a radius of over 1,360 solar radii. It is also 360,000 times more luminous than the Sun. ^[3] This star's spectral type is M0Ia, ^[6] meaning it possesses a cool temperature of below 3,800 K. So far, Trumpler 27-1 is the only identified red supergiant in the open cluster Trumpler 27.^{[ citation needed]}

Trumpler 27–1, and the open cluster in which it is located, is in the constellation of Scorpius.

• Westerlund 1-26
• RSGC1