Eta Ori
Observable Double Star
Fair (27/100)
Sep: 1.8", Companion: mag 4.9
HIP 25281; Eta Ori; 28 Ori
DoubleStar
Ori
Visible
Level 5
Expert level - Requires steady seeing
Physical Properties
Magnitude
3.36
Variable Type
Beta Cephei (Pulsating)
Spectral Type
B1 V +B2.
Star Color
Blue
(B-V -0.17)
Distance
1113.2 ly
Position & Identifiers
RA
05h 24m 28.6s
Dec
-02° 23' 49.0"
Constellation
Ori
HR
1788
HIP
25281
Bayer
Eta
Flamsteed
28 Ori
Variable ID
Eta Ori
Double Cat
4002
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Visibility
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Multiple Star System
Components
5
Component IDs
AB
Separation
1.8″
Companion Mag
4.9
Companion Sp
B2e
Position Angle
77°
Star Colors
A: Blue
B: Blue
Discoverer
DA 5
Eyepiece View
80x
Dawes: 1.9″
TFOV: 0.6°
Realistic = true angular size
Sep: 1.8″ · PA: 77° · N up, E left
Unresolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 3.1″
Size Comparison
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Stellar Lifecycle
Spectral Classification
Hertzsprung-Russell Diagram
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Blackbody Spectrum
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
Stellar Notes
EA + Beta C 3.31 - 3.60V, 3.14 - 3.35B, 7.989268d. Also sinusoidal pulsation period, amp. 0.05V, 0.30197 or 0.30145d.
ADS 4002A is SB triple system, abc with periods 9.2y and 7.989d. Speckle interferometry gives 9.219y, a = 0.036" for | for ab x c. Visual components AB, binary, 3.8, 4.8v, sep. 1.650"; C, 9.4v at 115". The total mass of the quintuple | system exceeds 50 solar masses, the most massive component being about 17 solar masses.
ab, 7.9841d, K 145.2k/s, V0 +35.9k/s, asini 15.9. abc, 9.2y, K 17.5k/s, V0 +19.5k/s, asini 805. Resolved by | speckle interferometry at 4-meter Mayall telescope, sep. 0.04"; vsini secondary 39k/s.
Ori OB1a; Orion belt; cluster CR 70.
0.005".
Expanding circumstellar shell.
Survey Image
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