10 Canis Majoris

10 Canis Majoris is a single^[14] variable star in the southern constellation of Canis Major,^[13] located roughly 1,980 light years away from the Sun.^[2] It has the variable star designation FT Canis Majoris; 10 Canis Majoris is the Flamsteed designation. This body is visible to the naked eye as a faint, blue-white hued star with a baseline apparent visual magnitude of 5.23.^[3] It is moving away from the Earth with a heliocentric radial velocity of +34 km/s.^[7]

10 Canis Majoris

A light curve for FT Canis Majoris from Hipparcos data, adapted from Lefèvre et al. (2009)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Major
Right ascension	06h 44m 28.46710s[2]
Declination	−31° 04′ 13.8923″[2]
Apparent magnitude (V)	5.23[3] (5.13–5.44)[4]
Characteristics
Spectral type	B2 V[5] or B2 IIIe[6]
B−V color index	−0.127±0.005[3]
Variable type	Be[4]
Astrometry
Radial velocity (Rv)	+34.0±4.2[7] km/s
Proper motion (μ)	RA: −3.286[2] mas/yr Dec.: +4.201[2] mas/yr
Parallax (π)	1.6454±0.0722 mas[2]
Distance	1,980 ± 90 ly (610 ± 30 pc)
Details
Mass	19.2±0.1[8] M☉
Radius	10.0[9] R☉
Luminosity	44,463+35,336 −19,689[10] L☉
Surface gravity (log g)	3.76±0.17[10] cgs
Temperature	25,350±1,030[10] K
Rotation	2.63 d[11]
Rotational velocity (v sin i)	205±5[12] km/s
Age	8.2±0.1[8] Myr
Other designations
10 CMa, FT Canis Majoris, CD−30°3484, GC 8827, HD 48917, HIP 32292, HR 2492, SAO 197149, CCDM 06445-3104, WDS J06445-3104[13]
Database references
SIMBAD	data

This is a massive Be star^[9] with a stellar classification of B2 V,^[5] matching a B-type main-sequence star. Hiltner et al. (1969) found a giant class of B2 IIIe,^[6] which is still in use with some studies.^[14][4] The star is spinning rapidly with a projected rotational velocity of 205 km/s^[12] and a rotational period of 2.63 days.^[11] This is giving it an oblate shape with an equatorial bulge that is 5% larger than the polar radius.^[15] The axis of rotation is inclined by an angle of 45° to the line of sight from the Earth.^[9]

In 1968, Alejandro Feinstein announced that the star is variable, based on observations from 1963-1965.^[16] It was given its variable star designation in 1973.^[17] Samus et al. (2017) classify it as a Be-type variable star that ranges from a peak visual magnitude of 5.13 down to 5.44 with a rotationally-modulated period of 2.63 days.^[4][11]

10 Canis Majoris is 8.2^[8] million years old with 19.2^[8] times the mass of the Sun and 10^[9] times the Sun's radius. It is radiating around 44,000^[10] times the luminosity of the Sun from its photosphere at an effective temperature of 25,000 K.^[10] There is a magnitude 12.58 visual companion at an angular separation of 37.3″ along a position angle of 99°, as of 2015.^[18]