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Star Spica guides you to Omega Centauri star cluster


Tonight for April 29, 2014

The sparkling blue-white star Spica can act as your guide to the Omega Centauri globular star cluster on these springtime nights. You can actually see this cluster with the unaided eye. Omega Centauri looks like a fairly faint (and possibly fuzzy) star. It’s a beautiful and very special star cluster, and Spica can help you find it.

Sky chart from our April 4 show showing how to follow the arc of the Big Dipper handle to Arcturus and Spica. At nightfall in late April and May, the Big Dipper appears higher up in the northern sky, but you still extend the arc of the Big Dipper handle to locate Arcturus and Spica.

To find Omega Centauri, first find Spica, the brightest star in the constellation Virgo the Maiden. You can spot the Spica by extending the curve of the Big Dipper handle, as illustrated on our chart to the right.

Spica transits – climbs to its highest point in the sky – around 11 p.m. local standard time (12 midnight daylight saving time) tonight 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 35o directly below Spica. A fist at an arm-length approximates 10o.

Omega Centauri star cluster. Image Credit: Jean-Paul Longchamp via Meade.com

Omega Centauri is special in part because you can see it with your eye alone. 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 globular and finest globular star cluster visible to the eye alone.

As darkness falls in late April and May, look for the upside-down Big Dipper way high up in your northern sky. Then follow the arc of the Big Dipper handle to Arcturus and Spica.

People living south of 35o north latitude have a realistic chance of spotting Omega Centauri, though it’s been seen as far north as Point Pelee, Canada (42o 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!

Bottom line: Use Spica to locate Omega Centauri on these springtime nights!

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