3 Monocerotis

3 Monocerotis is a binary star^[3] system in the equatorial constellation of Monoceros, located approximately 780 light years away from the Sun based on parallax.^[1] It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.92.^[2] The system is moving further from the Earth with a heliocentric radial velocity of +39 km/s.^[6]

3 Monocerotis

Location of 3 Monocerotis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Monoceros
Right ascension	06h 01m 50.42241s[1]
Declination	−10° 35′ 52.5565″[1]
Apparent magnitude (V)	4.92[2] (4.98 + 8.25)[3]
Characteristics
Spectral type	B5 III[4]
U−B color index	−0.58[5]
B−V color index	−0.12[5]
Astrometry
Radial velocity (Rv)	+39.00[6] km/s
Absolute magnitude (MV)	−1.94[2]
A
Proper motion (μ)	RA: −8.282[7] mas/yr Dec.: 4.385[7] mas/yr
Parallax (π)	4.5717±0.3115 mas[7]
Distance	710 ± 50 ly (220 ± 10 pc)
B
Proper motion (μ)	RA: 6.990[8] mas/yr Dec.: 4.574[8] mas/yr
Parallax (π)	3.1006±0.0960 mas[8]
Distance	1,050 ± 30 ly (323 ± 10 pc)
Details
3 Mon A
Mass	5.85[9] M☉
Radius	4.5[10] R☉
Luminosity	1,105[2] L☉
Temperature	15,000[9] K
Metallicity [Fe/H]	0.00[11] dex
Rotational velocity (v sin i)	45[12] km/s
Other designations
3 Mon, BD−10°1349, GC 7631, HD 40967, HIP 28574, HR 2128, SAO 151037, CCDM J06018-1036, WDS J06018-1036[13]
Database references
SIMBAD	data

The magnitude 4.98 primary, designated component A, has a stellar classification of B5 III,^[4] matching an evolved blue giant star. It has 5.85^[9] times the mass of the Sun and is radiating 1,105^[2] times the Sun's luminosity from its photosphere at an effective temperature of 15,000 K.^[9] The companion, component B, is magnitude 7.96 with an angular separation of 1.9″ from the primary.^[14]