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Jupiter and Spica to Omega Centauri

Chart at top via skyandtelescope.com

Tonight – April 16, 2017 – and throughout April and May, let the bright planet Jupiter and sparkling blue-white star Spica help you find the famous Omega Centauri star cluster. In 2017, Spica is easy to find because Jupiter is so bright and beams quite close to this star. In any year – even after Jupiter has moved away – Spica can help you find this cluster. That’s because, when Spica climbs highest up for the night, so does Omega Centauri. Follow the links below to learn more:

How can I find Jupiter and Spica, and then the cluster?

What if I’m in the Southern Hemisphere?

What is Omega Centauri?

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The Omega Centauri star cluster from Greg Hogan in Kathleen, Georgia. Thanks, Greg!

How can I find Jupiter and Spica, and then the cluster? Jupiter is easy. It’s the brightest starlike object in the night sky until Venus rises, shortly before dawn. Spica will be the nearest bright star to Jupiter.

In years when Jupiter is elsewhere, you can use the Big Dipper to find Spica. Just “follow the arc” in the Big Dipper’s handle to the bright orange star Arcturus, then “drive a spike” (keep extending that line) to Spica.

Extend the Big Dipper handle to arc to stars Arcturus and Spica. In 2017, the dazzling planet Jupiter helps guide your eye to Spica

Spica transits – climbs to its highest point in the sky – in the middle of the night in mid-April, for all locations around the globe. With each passing week, Spica will transit half an hour earlier. By mid-May, Spica will be transiting (appearing highest in the sky) around mid-evening (midway between sundown and midnight). You can find Spica’s (or Jupiter’s) precise transit time for your sky at the US Naval Observatory.

When Spica is highest in the south for Northern Hemisphere viewers, Omega Centauri is, too. When Spica is highest, look for Omega Centauri about 35o directly below it. A fist at an arm’s length approximates 10o.

You can see Omega Centauri with the unaided eye if your sky is dark enough and if you’re far enough south on the Earth. People living south of 35o North latitude have a realistic chance of spotting the cluster over the southern horizon, though we’ve seen at least one report of Omega Centauri seen as far north as Point Pelee National Park in Canada (42o north latitude). Omega Centauri looks like a fairly faint (and possibly fuzzy) star.

And, of course, it’s awesome from the Southern Hemisphere.

The globular cluster Omega Centauri — with as many as 10 million stars — is seen in all its splendor in this image captured from the European Southern Observatory’s La Silla Observatory in Chile.

What if I’m in the Southern Hemisphere? As seen from the Southern Hemisphere, Spica and Omega Centauri pass more nearly overhead. They still transit at approximately the same time (late evening in mid-April, mid-evening in mid-May). They’re still located about 35 o apart.

From the Southern Hemisphere, you’ve got a beautiful way to find this cluster. And, indeed, your view of the cluster will be better than ours in the north, because Omega Centauri will be higher in your sky.

To get in its general vicinity on the sky’s dome, look for the famous Southern Cross, which, officially, is the constellation Crux. Along the eastern edge of Crux is the dark Coalsack Nebula. Near the Coalsack – visible in binoculars – is the Jewel Box, an open star cluster with about 100 members, whose stars are colored red, white and blue.

If you can locate these objects, you’ll also find Omega Centauri. Consult the charts below for its location.

Chart via Space-Talk

Chart via Space-Talk

What is Omega Centauri? Omega Centauri is the largest and finest globular star cluster visible to the eye alone. Globular clusters are large, symmetrically shaped groupings of stars, fairly evenly distributed around the core of our Milky Way galaxy. Many northern stargazers have this particular cluster on their bucket lists.

Seeing Omega Centauri is very 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.

Like all globular clusters, Omega Centauri is best seen through a telescope. Then you see it as a globe-shaped stellar city, teeming with an estimated 10 million stars!

View larger. | Omega Centauri on March 14, 2016 by Rob Pettengill in Terlingua, Texas. Visit Rob Pettengill on Flickr.

View larger. | Omega Centauri in March, 2016 by Rob Pettengill in Terlingua, Texas.

Bottom line: From the Northern Hemisphere, you can use the star Spica in the constellation Virgo to locate Omega Centauri on springtime nights! From the Southern Hemisphere, star hop from the Southern Cross, to the dark Coalsack Nebula, to the Jewel Box star cluster, to Omega Centauri.

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Bruce McClure