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Zeta Aquarii — Double Star in Aquarius

HIP 110960; Zeta1 Aquarii; 55 Aquarii

Observable Double Star Excellent (66/100)

Sep: 2.5", Companion: mag 4.5

Magnitude 4.6m DoubleStar Aquarius (Aqr) Visible
Star Map
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Observe

1Physical Properties

Magnitude 4.59
Spectral Type F6IV subgiant
Distance 148 ly

2Position & Identifiers

RA 22h 28m 49.7s
Dec -00° 01' 13.0"
Constellation Aquarius (Aqr)
HR 8558
HIP 110960
HD 213051
SAO 146107
Bayer Zeta1
Flamsteed 55 Aqr
Double Cat 15971
SIMBAD Wikipedia

3How easy to split?

Primary 4.6 mag Companion 4.5 mag Separation 2.5″
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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. Hard+ Hard+ Hard+
150mm Newt. Easy Easy Easy
C8 203mm Easy Easy Easy
Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

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Best season Jul – Sep (peak: Aug)

5Multiple Star System Triple

Components 3 (triple)
Separation 2.5″
Companion Mag 4.5
Position Angle 154°
Star Colors B: Yellow-white
Discoverer STF2909
Binary with HR 8559, speckle interferometric sep. 1.672" (1982.38). B* 4.51, 12v, 25.5y, a = 0.072".

Separation over time

Period: 426.7 y Eccentricity: 0.300 Now: 2.5", PA 151° + 0.09" in 5 years
0.00" 0.80" 1.6" 2.4" 3.2" 2025 2030 2035 2040 2045 2.5"

Apparent separation over time, computed from ORB6 orbital elements. Steep curves indicate fast-changing pairs — catch them while they're splittable.

Eyepiece View

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80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E 154°

A: 4.6 · B: 4.5 · Sep: 2.5″ · PA: 154° · N up, E right

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″

Explore

6

Size Comparison

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7

Compare Stars

8

Spectral Classification

9

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map
10

Stellar Lifecycle

11

Blackbody Spectrum

12

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

13

Stellar Fusion

Discover

14Stellar Notes

Combined spectrum with HR 8559, F3IV-V.
0.040".
15

Light Travel Time Machine

16

Relativistic Travel

Nearby in the Sky

Other targets within a few degrees — pan your scope a little and keep exploring.

Visibility scores assume a 150 mm Newton at Bortle 4.

NGC 7391
Hard+
Elliptical galaxy
Galaxy mag 13.0 5.7° Aquarius
Show on Map

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