Sky ArchiveTonight

Find the Omega Centauri star cluster

Omega Centauri cluster, with an inset showing it larger.
View larger. | Omega Centauri star cluster, from Greg Hogan of Kathleen, Georgia. Thanks, Greg!

Tonight – or any night in the coming weeks – let the sparkling blue-white star Spica act as your guide to the Omega Centauri globular star cluster. You can see this cluster with the unaided eye, if your sky is dark enough. Omega Centauri looks like a fairly faint (and possibly fuzzy) star. It’s a beautiful and very special star cluster. In any year, Spica can help you find it.

To find Omega Centauri, first find Spica, the brightest star in the constellation Virgo the Maiden. How can you find it? Check out the chart below, and keep reading …

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Extend the handle of the Big Dipper to locate the stars Arcturus and Spica.
In any year, you can use the handle of the Big Dipper to locate the stars Arcturus and Spica.

Spica transits – climbs to its highest point in the sky – around 10 p.m local standard time (11 p.m. Daylight Saving Time) in mid-May for all locations around the globe. You can find Spica’s precise transit time for your sky at the US Naval Observatory.

As seen from the Northern Hemisphere, Spica and Omega Centauri transit due south at the same time. That means that – when Spica is highest in the south – Omega Centauri is, too. Look for Omega Centauri about 35 degrees directly below Spica. A fist at arm’s length approximates 10 degrees.

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Even at its highest, Omega Centauri is low in the south for Northern Hemisphere observers. But it’s conviently just below the bright star Spica. Finding Spica can lead you to this magnificent star cluster. Map via Sky&

Omega Centauri is special in part because you can see it with your eye alone, assuming you have a dark-enough sky. Very few of the Milky Way galaxy’s 250 or so globular star clusters are readily visible without optics. Globular clusters are large, symmetrically shaped groupings of stars, fairly evenly distributed around the core of our Milky Way galaxy. Omega Centauri is the largest and finest globular star cluster visible to the eye alone.

People living south of 35 degrees north latitude have a realistic chance of spotting Omega Centauri, though it’s been seen as far north as Point Pelee, Canada (42 degrees north latitude). Best appreciated with a telescope, Omega Centauri, the largest and brightest of all globular star clusters, is a globe-shaped stellar city, teeming with millions of stars!

Omega Centauri star cluster, the finest globular star cluster visible in Earth’s skies. Image via via

Bottom line: Use the star Spica in the constellation Virgo to locate Omega Centauri on these springtime nights!

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May 5, 2018
Sky Archive

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Bruce McClure

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