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Binocular Universe: Happy New Year
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Let's kick off the New Year and the first full month of winter by paying a call on some lesser known targets of the season. The subtle glow of the winter Milky Way, flowing southward from Gemini through Monoceros and into Canis Major, brings many star clusters that beckon our attention. Some of these are striking through binoculars, while others are a challenge just to see.
Above: Winter star map from Star Watch by Phil Harrington.
Above: Finder chart for this month's Binocular Universe.
Chart adapted from Touring the
Universe through Binoculars Atlas (TUBA)
Click the chart to display at full size. Chart will display in a separate tab.
This month, we'll focus on the area to the east-northeast of Sirius. The most prominent object in this portion of sky is open cluster M50. M50 was discovered by Charles Messier in April 1772, although historical records also suggest that it may have been seen by Giovanni Cassini (of Saturn's "Cassini's Division" fame) around 1711.
To find M50, let's use Sirius as our starting point. Viewing through your binoculars, trace a line from Sirius to Theta Canis Majoris. From Theta, continue on the same track an equal distance farther to the northeast, where you'll find our quarry. Through most binoculars, M50 will look like a small patch of celestial lint. Look carefully, and you should spot half a dozen or so of the 80 stars that call M50 home. Most appear white, but keep an eye out for a reddish star lying south of the cluster's.
Just west of M50, do you see a line of five 6th- and 7th-magnitude stars that meanders to the southeast? By following it along to the end, you'll find a pair of challenging NGC open clusters in the same field, just to the east. You likely won't see them at first, however. In fact, both will likely require giant binoculars for detection.
The first, NGC 2343, shines at 7th magnitude, but only measures 7 arc-minutes in diameter. Fifty-five stars call this cluster home, with the brightest shining at 8th magnitude. Through my 25x100 giants, the cluster is a distinct little knot of perhaps half a dozen points in a trapezoidal pattern.
Its neighbor, NGC 2335, appears a little larger, but is harder to spot owing to its fainter stars. None shines brighter than 10th magnitude. The stars' faintness combined with the richness of the surroundings give even my 25x100s a run for their money. But with patience, it does come through. These clusters are not true neighbors in space despite their closeness in our sky. NGC 2343 is estimated to be about 2,800 light years away, while NGC 2335 is more than 3,300 light years from us.
While not shown on the chart here, these clusters are engulfed in a large cloud of glowing hydrogen gas known as the Seagull Nebula. This is one of those "bright in photos, impossible by eye" objects, like the Horsehead Nebula in Orion. The brightest portion of the Seagull is its head, catalogued as IC 2177 and surrounding its ionizing star, HD 53367. In his book Hidden Treasures, author Steve O'Meara recounts how he has spotted the nebula "clearly with 7x50 binoculars and averted vision." Alas, I have not. Can you duplicate Steve's feat?
The rest of the surrounding region is sprawled with fainter tufts of nebulosity that collectively remind many of a seagull in flight, with wings stretched wide. If you are fortunate enough to be under dark, clear skies this winter, see if you can spot the full seagull.
If these prove a little too tough, then NGC 2353 should restore your faith. Set about 2 degrees due east of the last two clusters, NGC 2353 measures about 20' in diameter and contains 6th-magnitude SAO 152598, a monstrous blue-white giant star. The rest of the stars in the cluster pale in comparison, yet some are still bright enough to be resolvable in my 10x50s.
All three clusters belong to a region known as the Canis Major OB1 Association. Here, gas and dust, including the Seagull Nebula, is being compressed to form new stars. The trigger event that started the process is attributed to a supernova explosion that likely occurred a million years ago. SAO 152598, the beacon in NGC 2353, is the brightest, most massive star yet to be born in the region.
Next, give NGC 2345 a try. Here, sharp-eyed observers will spot a small "tuft" of unresolved stardust immediately south of 7th-magnitude HD 54494. While the glow of the cluster's 70 stars is evident, resolving individual suns here proves impossible through binoculars.
Finally, we have NGC 2360, lying about 3.5 degrees due east of Gamma Canis Majoris. The combined light of the 80 stars in NGC 2360 is evident through 10x50s if you use averted vision. In fact, you might even be able to just resolve a couple of the brightest stars buried within, since they teeter on 10th magnitude. The cluster overall shape appears distended, oriented east-west.
As you can see on the chart above and the list below, there are plenty of other targets in this area to challenge us and our binoculars. How many can you see? And if you need a respite from challenges, enjoy the beauty of M47, just along the eastern edge of this month's Binocular Universe, and M46 further east still. They vividly demonstrate just how different open clusters can be. If you wish to learn more about this odd couple, both were featured in this column back in March 2012.
We will continue exploring this region next month, so until then, always remember that for winter stargazing two eyes are better than one!
About the Author:
Phil Harrington has written 9 books on astronomy, including Star Ware, Star Watch, and his latest, Cosmic Challenge. Visit his web site, www.philharrington.net, for more information.
Phil Harrington's Binocular Universe is copyright 2015 by Philip S. Harrington. All rights reserved. No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.
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