Theta Canis Majoris

Theta Canis Majoris is a solitary,^[9] orange-hued star near the northern edge^[10] of the constellation Canis Major, forming the nose of the "dog".^[11] Its name is a Bayer designation that is Latinized from θ Canis Majoris, and abbreviated Theta CMa or θ CMa. The star is visible to the naked eye with an apparent visual magnitude of 4.08.^[2] Based upon an annual parallax shift of 12.07 mas as seen from Earth,^[1] it is located about 270 light years distant. The star is moving away from the Sun with a radial velocity of +96.2 km/s.^[5]

Theta Canis Majoris

Location of θ Canis Majoris (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Canis Major
Right ascension	06h 54m 11.399s[1]
Declination	−12° 02′ 19.06″[1]
Apparent magnitude (V)	4.08[2]
Characteristics
Evolutionary stage	Red giant branch[3]
Spectral type	K4 III[2]
U−B color index	+1.69[4]
B−V color index	+1.43[4]
Astrometry
Radial velocity (Rv)	+96.2±0.1[5] km/s
Proper motion (μ)	RA: −136.454 mas/yr[1] Dec.: −14.322 mas/yr[1]
Parallax (π)	12.0676±0.62 mas[1]
Distance	270 ± 10 ly (83 ± 4 pc)
Absolute magnitude (MV)	−0.36±0.15[6]
Details[5]
Mass	0.95±0.03 M☉
Radius	33.01±0.75[7] R☉
Luminosity	304.9±7[7] L☉
Surface gravity (log g)	1.67±0.08 cgs
Temperature	4196±43[7] K
Metallicity [Fe/H]	−0.52±0.04 dex
Rotational velocity (v sin i)	2.72±0.40 km/s
Age	10.41±1.31 Gyr
Other designations
θ CMa, 14 Canis Majoris, BD−11°1681, FK5 266, GC 9051, HD 50778, HIP 33160, HR 2574, SAO 152071[8]
Database references
SIMBAD	data

This is a evolved K-type giant star with a stellar classification of K4 III,^[2] having exhausted the supply of hydrogen at its core then expanded. Theta Canis Majoris is 5% less massive than the Sun,^[5] but has grown to 33 times the Sun's girth.^[7] This star is around ten billion years old,^[5] over twice the age of the Solar System.^[12] It radiates 305 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,200 K.^[7] This temperature gives it the cool orange hue of a K-type star.^[13]