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Binocular Universe: All Pooped Out

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Binocular Universe: All Pooped Out

March 2015


Phil Harrington

With March comes the promise of winter's end and the return of warmer temperatures.  As the northern hemisphere transitions to spring, let's head south one more time to enjoy some little known binocular targets.


The constellation Puppis occupies much of our late winter southern sky.  But thanks to its low altitude for most of us, coupled with the fact that only one of its stars reaches 3rd magnitude, Puppis usually sails past without much notice.

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.


Puppis was originally just one part of a huge constellation called Argo Navis.  Although it never rose much above the southern horizon from mid northern latitudes, Argo Navis contained over 800 naked eye stars within its huge borders.  Due to its vast extent, the constellation was subdivided in 1752 by the French astronomer Nicolas Louis de Lacaille into four component constellations.  Today, we know them as Puppis the Stern, Pyxis the Compass, Vela the Sails, and Carina the Keel.


The story behind the constellation is interesting in its own right.  You may be familiar with the tail of the mythological ship Argo and how it was built by Argos for Jason.  Jason then set sail along with a crew of 50 Argonauts in search of the Golden Fleece.  In Greek mythology, the Golden Fleece was a symbol of authority and kingship. Jason went after the fleece in order to attain his birthright position of king of Iolcus in Thessaly. Jason assembled a colorful crew to aid in his quest, including the twin brothers Castor and Pollux of Gemini fame.


The ship Argo took Jason and his crew on many adventures along the way.  Against long odds, they successfully returned with the Golden Fleece. When their voyage was over, Athena placed the ship in the sky. But things didn’t end happily ever after for Jason. He was unfaithful to his wife, the enchantress Medea, whom he had met during his voyage. Without getting into all the sorted details, suffice it say that he died lonely and unhappy. The story goes that he was asleep under the stern of the rotting Argo when it fell on him, killing him instantly.


For dwellers of the northern hemisphere, Puppis is the most familiar part of the fragmented Argo Navis.  It lies east of Canis Major, in an area notably absent of any bright stars.   Although it lacks naked eye luster, Puppis is rich in deep-sky treasures.  We have already surveyed many of these in past columns.  You might revisit those (March 2012 and February 2014) before continuing below.  This month, we will bounce around to pick up the leftovers missed in those previous encounters.


L2 Puppis, also known as HD 56096, is a striking red type-M sun found about 12 degrees northeast of brilliant Canopus.  Classified as "semi regular," L2 flickers between magnitudes 2.6 and 6.2.  Its remarkable brightness shift makes this an ideal star for study through binoculars, or even with the naked eye at times. Observers should note that the listed period of 140 days is merely an average.  The actual time span between maxima or minima can vary greatly.  These wild fluctuations in brightness are believed to be a combination of pulsations of the star itself as well as broad circumstellar clouds of opaque dust belching out and hiding some of the disk from view.


Haffner 13 appears as a small knot of stars in western Puppis.  Fifteen suns are believed to belong to this group, but only seven are bright enough to be clearly seen through binoculars.  Unfortunately, the star fields which enclose Haffner 13 are almost as rich as the cluster itself, making positive identification difficult.  As an aid, look about 1o southwest of 3 Puppis for a close set pair of 8th magnitude stars, with a lone 7th magnitude point of light just to their southwest.  All three of these stars are located within the cluster.


If Haffner 13 proves too difficult to identify, you may have better luck with NGC 2439, located about 1.5 degrees due south.  To find it, draw a line from Wezen (Delta Canis Majoris) through Aludra (Eta Canis Majoris). Continue the line about an equal distance in the same direction and you'll be within striking distance of NGC 2439.


Studies show that 80 stars join to form this 10 arc minute diameter open cluster, although most are too faint to be seen in binoculars.  Through most glasses, NGC 2439 appears as a 7th-magnitude glow peppered with a single bright star and a few fainter points.  The brightest star in the cluster is golden R Puppis.  Though known to be a semi regular variable, it fluctuates with great subtlety between magnitudes 6.6 and 6.9.


Ruprecht 56 hugs the southern border of Puppis, within a stellar triangle that includes 2nd-magnitude Zeta Puppis.  Earth based observers see this open cluster as a relatively loose gathering of 40 stars of 8th magnitude and fainter spread across nearly 3/4o.  Although the dimmest cluster stars are undetectable in binoculars, 15 suns shine forth in 7x glasses if the cluster is high enough above the horizon.  Helping us pinpoint the exact location of Ruprecht 56 is 3rd magnitude h2  Puppis superimposed on the cluster's eastern border.  Apparently this association is not a physical one, as the star seems to be only a chance foreground object.


Before you move on, pause at Zeta Puppis to consider what you are seeing.  Zeta, classified as spectral type O4, is one of the hottest and most luminous stars visible to the naked eye. It is one of the closest of its kind to Earth, although it is still more than 1,000 light years away. Its overall luminosity, or true energy output, tops our Sun's by more than 10,000 times, with a surface temperature estimated to be 40,000+ K.


Finally, here’s a suitable challenge for 70-mm and larger binoculars that comes from the Saguaro Astronomy Club’s asterism database.  They credit South African amateur astronomer and author Magda Streicher as the first person to notice a small 5-star asterism that is reminiscent of a miniaturized Cassiopeia.  Sure enough, if you center your attention at RA 08h 08.0m, Dec. -15° 11’, you’ll find her. Bear in mind, however, that this queen only measures 7’ long by 2’ wide. I’ve spotted it with my 16x70s, but I suspect that it would be a daunting task with less magnification.


Look at what else awaits you in this month's Binocular Universe!  That should keep you busy for the rest of the winter.

Next month, we head back north to more familiar surroundings.  Until then, enjoy the challenge of the far southern sky. And remember that 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.


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