Messier’s “Lost” Star Cluster
Like many constellations this time of year, Hydra contains mostly galaxies. The venerable Burnham’s Celestial Handbook lists some 60 galaxies in this long constellation. But most are dim… less than magnitude 12 and quite hard to see with scope smaller than 10″. And since Hydra sports few bright stars, many casual observers pass by Hydra in search of better sights.
Which is unfortunate. Because there are a few memorable bright deep-sky objects nestled in the great sky serpent. One of the prettiest is the oft-overlooked open star cluster M48. This cluster, along with M44 and M67 in Cancer just 10 degrees north, make for a pleasant short observing session on an April weekend with binoculars or a small scope.
To find Messier 48, look about 10 degrees southwest of Hydra’s head, and 10 degrees southeast of the bright star Procyon. (Remember that 10 degrees is about the width of your fist held at arms length). About 8 degrees southwest of the head, look for the 4th magnitude star C Hydrae; M48 is 2.5 degrees southwest of this star. It should fit in the same field of view of binoculars or your finderscope. You may even see the cluster with the unaided eye if your sky is clear and dark. At magnitude 5.8, it’s just on the edge of visibility as a large fuzzy patch about the size of the full moon.
*** Highly Recommended ***
Online astronomy course helps you wield your telescope like a pro. Insider tips and techniques from a renowned astronomy expert. Instant download. Click here to learn more…
* * * * * * * * * *
M48, bottom-center, just a few degrees southwest of C Hydrae
In a telescope at 40-50x, M48 is a pleasing sight . You’ll see 80-100 stars of 8-12th magnitude spread over a full degree of sky in a distinctly wedge-shaped pattern, with a dark keyhole-shaped notch at the base of the wedge. The brightest star, at the southeast edge, appears yellow-white. A detailed analysis of the star colors and brightness suggests the cluster is some 300 million years old. M48 lies some 2,000 light years away.
Charles Messier observed M48 in 1771, and noted the position in his catalog. But later astronomers could find no cluster at the coordinates Messier recorded. Did the star cluster disappear? Likely not. As it turns out, Caroline Herschel recorded a star cluster, now known as NGC2548, about 5 degrees south of Messier’s position for M48. Astronomy historians agree that Messier observed NGC2548 and simply erred when determining its position.
And yet…
Astronomy writer Steven James O’Meara writes in his excellent book The Messier Objects, that when observing M48, he noticed with his unaided eye a fuzzy patch about 5 degrees southeast of M48… the location originally recorded by Messier. He casually mistook this patch for M48, but when he observed it with his telescope, it was not visible. With binoculars slightly de-focused, the patch look fuzzy and cluster-like, though he determined it’s really just a group of unassociated stars. To the unaided eye, this mystery patch was actually brighter than M48 according to the sharp-eyed O’Meara.
Is this patch what Messier saw and recorded as M48?
Try to see this little patch for yourself as you look for M48 this weekend.
