Theta¹ Orionis D

Theta¹ Orionis D (θ¹ Orionis D) is a member of the Trapezium open cluster that lies within the Orion Nebula. It is a B class blue main sequence star with several faint companions.

θ¹ Orionis D

Theta1 Orionis D and companions in the Trapezium cluster
Observation data Epoch J2000      Equinox J2000
Constellation	Orion
Right ascension	05h 35m 17.24645s[1]
Declination	−05° 23′ 16.5707″[1]
Apparent magnitude (V)	6.70[2]
Characteristics
Spectral type	B1.5 Vp[3]
U−B color index	−0.71[2]
B−V color index	+0.09[2]
Astrometry
Radial velocity (Rv)	+32.4[4] km/s
Proper motion (μ)	RA: +1.822[1] mas/yr Dec.: _0.393[1] mas/yr
Parallax (π)	2.2820 ± 0.0207 mas[1]
Distance	1,430 ± 10 ly (438 ± 4 pc)
Absolute magnitude (MV)	−3.3[5]
Details
Mass	18±6[5] M☉
Radius	5.6±0.8[5] R☉
Luminosity	29,500[5] L☉
Surface gravity (log g)	4.2±0.1[5] cgs
Temperature	32,000±1,000[5] K
Rotational velocity (v sin i)	49.0±0.9[5] km/s
Age	2.5±0.5[5] Myr
Other designations
θ1 Orionis D, 41 Orionis D, HR 1896, HD 37023, HIP 26224, WDS J05353-0523D
Database references
SIMBAD	data

θ¹ Orionis consists of multiple components, primarily the four stars of the Trapezium cluster (A, B, C, and D) all within one arc-minute of each other. θ² Orionis is a more distant grouping of three main stars plus several fainter companions, 1-2 arc-minutes from θ¹.

θ¹ D itself has a faint optical companion 1.4" away and a spectroscopic companion in a 40-day orbit. Infrared Optical Telescope Array observations suggest another companion at 18.6 mas.^[6]