Sigma Aquarii — Double Star in Aquarius

Observable Double Star Good (57/100)

Sep: 3.7", Companion: mag 8.5

Magnitude 4.8^m DoubleStar Aquarius (Aqr) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.82

Spectral Type A0IV s subgiant

Star Color Blue-white (B-V -0.06)

Distance 155 ly

2Position & Identifiers

RA 22h 30m 38.8s

Dec -10° 40' 41.0"

Constellation Aquarius (Aqr)

HR 8573

HIP 111123

HD 213320

SAO 165134

Bayer Sigma

Flamsteed 57 Aqr

3How easy to split?

Primary 4.8 mag Companion 8.5 mag Separation 3.7″

Sign in and configure your equipment and default location to see a personalized row.

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Hard	Hard	Hard
150 mm Newton 150mm Newt.	Medium+	Medium+	Medium+
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

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

4Visibility

Set a location in User Settings to see visibility data.

Best season Jul – Sep (peak: Aug)

5Multiple Star System

Separation 3.7″

Companion Mag 8.5

Position Angle 10°

Star Colors A: Blue-white B: Yellow

Discoverer HDS3190

Eyepiece View

Telescope Eyepiece

Log in to set your own equipment

80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.8 · B: 8.5 · Sep: 3.7″ · PA: 10° · N up, E right

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

Explore

6

Size Comparison

Querying VizieR for stellar data…

7

Compare Stars

Compare with another star

8

Spectral Classification

9

Hertzsprung-Russell Diagram

Loading HR diagram…

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

Group/Cluster

In Ursa cluster?

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.

Elliptical galaxy

Galaxy mag 12.1 3.5° Aquarius

Eclipsing binary, period 22.7h

Double Star mag 6.37 9.3° Aquarius

Explore Nightbase

Related knowledge, tools, and stories — no observation planning required.

Double Stars — A Guide for Observers

Two suns where one appeared — how to find, split, and appreciate the night sky's finest pairs. From Albireo's gold-and-blue to the Sirius B challenge.

Mythology, bright stars, and deep-sky highlights.

Polar caps, dust storms, and observing its oppositions.

}