Eta Orionis

η Orionis
Location of η Orionis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 24m 28.61672s[1]
Declination −02° 23′ 49.7311″[1]
Apparent magnitude (V) 3.42[2] (4.50 + 5.90 + 5.65 + 4.95)[3]
Characteristics
Spectral type Aa: B1 V
Ab: B3 V
Ac: B3 V
B: B2 V[3]
U−B color index −0.90[2]
B−V color index −0.17[2]
Variable type Algol[4]
Astrometry
Radial velocity (Rv)+19.8[5] km/s
Proper motion (μ) RA: −0.71[1] mas/yr
Dec.: −3.46[1] mas/yr
Parallax (π)3.34±1.07 mas[1]
Distanceapprox. 1,000 ly
(approx. 300 pc)
Orbit
PrimaryAa
CompanionAb
Period (P)7.98763(22)[6] days
Eccentricity (e)0.0095±0.0010[6]
Inclination (i)87.62±0.42[6]°
Argument of periastron (ω)
(primary)
164±18[6]°
Semi-amplitude (K1)
(primary)
145.5±0.03[7] km/s
Semi-amplitude (K2)
(secondary)
150±3[7] km/s
Orbit[3]
CompanionAc
Period (P)9.442±0.012 yr
Semi-major axis (a)0.0441±0.0015
Eccentricity (e)0.45±0.02
Inclination (i)102.8±1.8°
Details
η Ori Aa
Mass10.87±0.44[6] M
Radius6.477±0.073[6] R
Surface gravity (log g)3.851±0.010[6] cgs
Temperature26,600[7] K
Rotational velocity (v sin i)20[7] km/s
η Ori Ab
Mass10.54±0.22[6] M
Radius4.79±0.10[6] R
Surface gravity (log g)4.100±0.016[6] cgs
Temperature25,950[6] K
Rotational velocity (v sin i)130[7] km/s
η Ori Ac
Mass6.78[8] M
η Ori B
Mass8.7[8] M
Other designations
η Ori, 28 Orionis, BD−02°1235, HD 35411, HIP 25281, HR 1788, SAO 132071[9]
Database references
SIMBADdata

Eta Orionis or Algjebbah,[citation needed] Latinized from η Orionis, is a multiple star in the constellation Orion. It lies a little to the west of Orion's Belt between Delta Orionis and Rigel, being closer to Delta Orionis than to Rigel. It lies at a distance of around 1,000 light-years from Earth and is part of the Orion OB1 association.

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  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).

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