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Caldwell 80 — Globular Cluster in Centaurus

NGC 5139

Globular Cluster Showpiece (95/100)
Magnitude 3.9m GlobularCluster Centaurus Visible
Credit: Chuck Ayoub. License: CC0. (Wikimedia Commons)
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About Omega Centauri

Description

Omega Centauri (NGC 5139) is the largest and brightest globular cluster in the Milky Way, located about 15,800 light-years away in Centaurus. Spanning 36 arcminutes and containing roughly 10 million stars, it is visible to the naked eye at magnitude 3.9.

Observing Tips

One of the most spectacular objects in the sky. Visible to the naked eye as a fuzzy star. Binoculars show it as a large, bright, granular ball. Any telescope resolves it beautifully into a sea of stars. Best from southern latitudes in spring and summer — a must-see object.

History

Known since antiquity. Ptolemy cataloged it as a star in 150 AD. Edmond Halley recognized its non-stellar nature in 1677. It is now believed to be the stripped core of a dwarf galaxy that was absorbed by the Milky Way.

Fun Facts

Omega Centauri has multiple stellar populations with different ages and metallicities, unlike normal globular clusters. This is strong evidence that it is the nucleus of a dwarf galaxy consumed by the Milky Way. It may contain an intermediate-mass black hole of about 40,000 solar masses at its center.

Observe

1Properties

Magnitude 3.9
Angular Size 27.0′
Distance 17,300 ly
Globular Cluster [Distance: 17300 ly]

Position & Identifiers

RA 13h 26m 47.3s
Dec -47° 28' 48.0"
Constellation Centaurus
Catalog C80
Also known as NGC 5139
Physical size
49 light-years across — about 5.7× the Sun-to-Sirius distance

2How easy to spot?

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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. Easy Easy Easy
150mm Newt. Easy Easy Easy
C8 203mm Easy Easy Easy
Easy Medium Hard Very hard Impossible

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

Easy on Seestar S50

3Visibility

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Best season Mar – May (peak: Apr)

4 Eyepiece View

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50x TFOV: 1.0° Lim. mag: 13.6
N E

Omega Centauri · 27.0′ diameter · N up, E left

5 Best Magnification

6Metallicity

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 Ancient halo Disc / bulge M92 M71 NGC 6441 Omega Centauri [Fe/H] = -1.53

[Fe/H] = -1.53 — these stars formed from gas about 34× poorer in iron than the Sun.

7Concentration class

I II III IV V VI VII VIII IX X XI XII Dense (I) Loose (XII) V Core / half-light / tidal tidal 48.4′ half 5.0′ core 2.37′

Shapley-Sawyer class V — moderately concentrated core.

Explore

8 Classification Decoder

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9

Light Travel Time Machine

10

Relativistic Travel

Community Photos (1)

Credit: Chuck Ayoub. License: CC0. (Wikimedia Commons)

Credit: Chuck Ayoub. License: CC0. (Wikimedia Commons)

Skybred Mar 2, 2026

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 5206
Easy
Elliptical galaxy
Galaxy mag 10.49 1.3° Centaurus
V744 Cen
Easy
Semi-regular variable, range 5.1–6.5
Variable Star mag 6.00 3.3° Centaurus
NGC 5286
Easy
Globular cluster — dense ball of ancient stars
Globular Cluster mag 7.6 5.0° Centaurus
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