Alcyone
HIP 17702; Eta Tau; 25 Tau
Observable Double Star
Good (52/100)
Sep: 117.6", Companion: mag 6.3
HIP 17702; Eta Tau; 25 Tau
DoubleStar
Tau
Visible
Level 2
Small telescope (4") - Requires steady seeing
Physical Properties
Magnitude
2.87
Spectral Type
B7III
Star Color
Blue-white
(B-V -0.09)
Distance
407.7 ly
Position & Identifiers
RA
03h 47m 29.1s
Dec
+24° 06' 18.0"
Constellation
Tau
HR
1165
HIP
17702
Bayer
Eta
Flamsteed
25 Tau
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Visibility
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Multiple Star System
Components
5
Component IDs
O
Separation
117.6″
Companion Mag
6.3
Companion Sp
A4V
Position Angle
291°
Star Colors
A: Blue-white
B: White
Discoverer
STFA 8
Eyepiece View
80x
Dawes: 1.9″
TFOV: 0.6°
Realistic = true angular size
Sep: 117.6″ · PA: 291° · N up, E left
Resolved · 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
Component A is occultation double, sep. 0.031". B, C, D, 8.1 A0V, 8.1 Am(A5/F0/F2) and 8.7v F2V at 117" to 190". | Possibly second occultation companion at 0.001", unresolved by speckle interferometry. vsini of B 155k/s. Numerous | photometric determinations yield 6.3 for B component. The HD gives 8.1 for 23629 and the IDS indicates 8.1. Burnham, | Double Stars, gave 7.0 vis.
Color excess E(B-V) = +0.03.
Pleiades cluster; Mel 22 #1432; in reflection nebula; Pleiades nebula; member assoc. Tau R1 at 110 pc.
Rotationally unstable Be shell star.
ALCYONE. The brightest of the Pleiades.
Angular diameter = 0.0016".
Survey Image
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