Tau Canis Majoris

Tau Canis Majoris
Location of τ CMa (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension 07h 18m 42.48642s[1]
Declination −24° 57′ 15.7413″[1]
Apparent magnitude (V) 4.40[2] (4.89 + 5.33 + 9.70[3])
Characteristics
Spectral type O9II[4] (O9II + B0.5V + B0.5V[5])
U−B color index −0.99[2]
B−V color index −0.15[2]
Variable type β Lyr[6]
Astrometry
Radial velocity (Rv)+33.80[7] km/s
Proper motion (μ) RA: −2.31[1] mas/yr
Dec.: 5.02[1] mas/yr
Parallax (π)1.09 ± 0.59 mas[1]
Distance1,570[8] pc
Absolute magnitude (MV)−5.9 + −3.6 + −3.6[5]
Details
τ CMa Aa
Mass50[9] M☉
Radius19.8[10] R☉
Luminosity280,000[11] L☉
Surface gravity (log g)3.5[10] cgs
Temperature32,000[11] K
τ CMa Ab1
Mass17.8[9] M☉
τ CMa Ab2
Mass17.8[9] M☉
Other designations
30 Canis Majoris, HR 2782, HD 57061, CD−24°5176, HIP 35415, SAO 173446, GC 9736, ADS 5977, CCDM 07187-2457
Database references
SIMBADdata

Tau Canis Majoris (τ CMa, τ Canis Majoris, 30 CMa) is a multiple star system in the constellation Canis Major. It is approximately 5,000 light years distant from Earth and is the brightest member of the open cluster NGC 2362.

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