RT Carinae

RT Carinae, also known as CD-58 3538, is a red supergiant and a variable star, located 7,000 light years away in the constellation Carina. It is in the Carina Nebula. The average apparent magnitude of +8.55, too faint to be visible to the naked eye.

RT Carinae

RT Carinae is the bright orange star south of the Trumpler 15 cluster.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Carina
Right ascension	10h 44m 47.148s[1]
Declination	−59° 24′ 48.1228″[1]
Apparent magnitude (V)	8.36[2] (8.2 - 9.9[3])
Characteristics
Spectral type	M2+ Iab[4]
B−V color index	+2.31[2]
Variable type	LC[3]
Astrometry
Radial velocity (Rv)	−21.95±0.58[1] km/s
Proper motion (μ)	RA: −7.432 mas/yr[1] Dec.: 2.851 mas/yr[1]
Parallax (π)	0.470±0.069 mas[5]
Distance	approx. 7,000 ly (approx. 2,100 pc)
Absolute magnitude (MV)	−6.74[2]
Details[2]
Radius	1,090 R☉
Luminosity (bolometric)	129,000+33,000 −24,000[6] L☉
Surface gravity (log g)	−0.3 cgs
Temperature	3,625 K
Other designations
RT Car, HD 303310, HIP 52562, SAO 238424, CD−58°3538, AAVSO 1040-58
Database references
SIMBAD	data

Characteristics

RT Carinae is a red supergiant with a spectral type of M2+ Iab^[4] and has a temperature of 3,660 K. It is about 1,090 times larger than the Sun^[2] and is estimated to be 130,000 times more luminous.^[6] It is close to the open cluster Trumpler 15, but is not thought to be a member.^[7] It appears to be surrounded by a dusty nebula, possibly material ejected from the star itself.^[8]

A visual band light curve for RT Carinae, plotted from ASAS data^[9]

In 1898 it was announced that Louisa D. Wells had discovered that the star's brightness varies. The initial variable star designation given was R Carinae, but that name was eventually given to a different star.^[10] It appears with its current name, RT Carinae, in Annie Jump Cannon's 1907 work, Second Catalogue of Variable Stars.^[11] It is catalogued as an irregular variable star, but a number of possible pulsation periods have been detected. Analysis from observations over 40 years give variations with periods of 201 and 448 days, with other studies suggesting periods of 100 and 1,400 days.^[12]