Theta1 Orionis D

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

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 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]

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Observation data Epoch J2000 Equinox J2000
Theta¹ Orionis D and companions in the Trapezium cluster
Constellation	Orion
Right ascension	05^h 35^m 17.24645^s^[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 (R_v)	+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 (M_V)	−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

Theta1 Orionis D

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