From the March 2009 issue

Free preview: Phil Harrington’s Binocular Universe, “Survey the southern sky”

Two deep-sky objects in Centaurus challenge Northern Hemisphere observers.
By | Published: March 23, 2009
Phil Harrington
Phil Harrington’s Binocular Universe was a monthly column in Astronomy magazine. This article appeared in March 2009. Subscribers have access to the complete online archive of “Phil Harrington’s Binocular Universe.” Subscribe today!

On August 4, 1826, Scottish astronomer James Dunlop discovered what would prove to be a puzzle for the ages. While observing with his 9-foot reflecting telescope from Parramatta, New South Wales, Dunlop found what he later described as “a very singular double nebula. … These two nebulae are completely distinct from each other, and no connection of the nebulous matters between them.” A singular double nebula? Sounds more like an astronomical oxymoron than an observation. What had Dunlop found?

Dunlop’s riddle is now known as Centaurus A (NGC 5128), a fascinating galaxy in the southern constellation Centaurus the Centaur. When we look at Centaurus A, we are looking at a case of galactic cannibalism. Inside the heart of this huge elliptical galaxy lies a massive black hole that is consuming a smaller spiral galaxy. The two are believed to have collided between 160 and 500 million years ago.

Your binoculars won’t detect any of the internal strife that Centaurus A is enduring, but they can show you this intergalactic enigma that continues to fascinate astronomers — that is, if you can see the galaxy at all. The problem is that Centaurus A lies 43° south of the celestial equator, and so it is always confined to the far southern sky for most of the Northern Hemisphere. It never rises more than 7° above my own horizon here on Long Island (40° north latitude). Farther north, its maximum altitude shrinks; travel southward and Centaurus A will climb higher in the sky.

Overlooking the Atlantic Ocean along Long Island’s south shore, I can just make out Centaurus A through my 10×50 binoculars. It’s tough, but by waiting until it lies on the meridian and is highest in the sky, it’s unmistakable.

As luck would have it, the bright star Spica (Alpha [α] Virginis) has nearly the same right ascension as the galaxy, so we can use it as a guide. Scan about 12° (two fields of view) straight southward from Spica to 3rd-magnitude Gamma (γ) Hydrae. Another 13° farther south, you will come to 3rd-magnitude Iota (ι) Centauri. It won’t be long now.

May 2009 Harrington column
Centaurus lies in the far southern sky for people in the Northern Hemisphere. Spotting the constellation’s two deep-sky targets, Centaurus A and Omega (ω) Centauri, is a good challenge for binocular observers.
Astronomy: Roen Kelly
Look for the 4th-magnitude star HD 117440 to Iota’s southeast and then a distinctive triangle of stars — formed from Nu (ν), Mu (μ), and Phi (φ) Centauri — farther southeast still. Those latter three suns all lie at the same declination as the galaxy, so if you can see them, the galaxy is waiting for you. Place HD 117440 on the northern edge of your binocular field and Nu and Mu toward the east. Look carefully along the western side of the field and you should see the galaxy’s faint, fuzzy disk. With 70mm and larger binoculars, you might be able to glimpse the mysterious dark band that slices across the galaxy.

If you found Centaurus A, then the night sky’s grandest globular cluster of all, Omega (ω) Centauri (NGC 5139), lies just 4½° farther south. Can you spot it, too? I’ve seen 2nd-magnitude Zeta (ζ) Centauri, which lies at the same declination as Omega, from Long Island but never the cluster itself.

From a vantage point that places it high in the sky, Omega Centauri is a sight to behold. The finest view I have ever had was from the Winter Star Party in the Florida Keys several years ago. It was absolutely stunning! My first thought when I saw it: It’s huge! I could resolve some of its estimated 1 million stars with 11×80 binoculars, while a “not-quite-resolved” grainy appearance was plainly evident through 10x50s. Regardless of the instrument used to spot it, you’ll remember your first encounter with Omega Centauri for a lifetime.

This month concludes my “Binocular Universe” column here in Astronomy magazine. I hope you have enjoyed the journeys we have shared over these past 4 years and that you will continue to tour the universe through binoculars far into the future. Let’s keep in touch. Drop me a line at and share your observations. And until we meet again somewhere under the stars, remember that, now as always, two eyes are still better than one.

This month’s Web Extra
More southern-sky treasures.

Read more of Phil Harrington’s Binocular Universe
April 2009: Comb through Coma Berenices
See an archive of Phil Harrington’s binocular universe