When is the best time to observe 3 Centauri?

3 Centauri is best observed from March through May, with peak visibility during April when it transits around midnight in the Northern Hemisphere.

Where is 3 Centauri located in the sky?

3 Centauri lies in the constellation Centaurus at right ascension 13h 52m and declination -32° 60′.

What telescope do I need to split 3 Centauri?

Splitting 3 Centauri requires an aperture of roughly 80 mm or larger — the components are separated by about 7.8″ at magnitudes near 4.6. Larger apertures and steady seeing help resolve the pair cleanly.

3 Centauri — Double Star in Centaurus

Observable Double Star Excellent (65/100)

Sep: 7.8", Companion: mag 6.0

Magnitude 4.6^m DoubleStar Centaurus (Cen) Visible

Star Map + List + Plan

Observe

1Physical Properties

Magnitude 4.56

Spectral Type B5IIIp bright giant

Star Color Blue-white (B-V -0.13)

Distance 192 ly

2Position & Identifiers

RA 13h 51m 49.6s

Dec -32° 59' 40.0"

Constellation Centaurus (Cen)

HR 5210

HIP 67669

HD 120709

SAO 204916

Flamsteed 3 Cen

SIMBAD

3How easy to split?

Primary 4.6 mag Companion 6.0 mag Separation 7.8″

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Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
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

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Best season Mar – May (peak: Apr)

5Multiple Star System

Separation 7.8″

Companion Mag 6.0

Companion Sp B8V

Position Angle 105°

Star Colors A: Blue-white B: Blue-white

Discoverer H 3 101

Notes

Mag. for combined light with HR 5211, 4.32V. Probably not binary.

Separation over time

Measured 1783 → 2015 (232 y)

Separation drift 11.6" → 7.8" (-3.80")

Rate -0.0164" / y

PA drift 112° → 105° (-7°, -0.030°/y)

Apparent motion is significant on a human timescale — worth revisiting in a decade.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.

Eyepiece View

Telescope Eyepiece

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 4.6 · B: 6.0 · Sep: 7.8″ · PA: 105° · N up, E right

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

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Size Comparison

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Spectral Classification

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Hertzsprung-Russell Diagram

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

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Stellar Lifecycle

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Blackbody Spectrum

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Stellar Absorption Spectrum

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

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Stellar Fusion

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14Stellar Notes

Group/Cluster

Sco-Cen cluster; Sco-Cen stream; member of the local association (Pleiades group); upper Cen group of Sco-Cen assoc.; | member of Pleiades group.

Spectral

Strong phosphorus. Abnormally weak helium. 3 Cen A shows excess of phosphorus by factor of 100, krypton by 1000, gallium | by 10,000, and deficiencies of sulphur and helium.

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