M5 Globular Cluster in Serpens and The Mystery of The Ruby Eyes

     Each and every spring I always try to observe the magnificent globular cluster M5, in hopes to see a long held mystery, referred to as the Ruby Eyes. 

     My hope for all reading this, you’ll give this challenge a try, especially if you have a larger aperture telescope (16-inches and above.)   

     In the early 90’s, during astronomy conventions and other in my area, there were many discussions of the “Ruby Eyes of M5” and the mystery behind them. 

     What did Bill Henson and Arlo Gardner see on that night in July 1992?  A few of us attempted to find out in May and June of 2016, using the Observer’s Challenge platform.    

Sky & Telescope, December 1993, page 108: A brief and paraphrased account from the original article:

     On July 17, 1992, North Carolina amateurs Bill Henson and Arlo Gardner were testing Gardner’s newly rebuilt 20-inch Dobsonian. While sweeping through Serpens, they picked up the mag. 6 globular cluster M5. Taking time to examine the cluster’s tight, compact core, they both noticed a pair of ruby stars south-southeast of the cluster’s center and oriented east-west. “They impressed us because of their color,” writes Henson. “In fact, the pair actually seemed closer than the globular….suspended between us and M5.” They estimated the stars to be around mag. 13, separated by about 30 to 40 arc seconds.

     Tom English, spearheaded this review, and what I think was a very objective study.  James Dire also played a very significant and important role in this project with his help in imaging M5 at that time.  Sue French also contributed with her own research concerning the variability of the “two subject” stars. 

     Unfortunately one of the amateurs that reported this sighting of red stars, Bill Henson has since passed away, but not too late to learn of this review.  Bill was appreciative for all that took their time and effort to bring back to life, the “Ruby Eyes” that he and his observer friend, Arlo Gardner reported on a special night so many years earlier.    

     This causes me to feel good and with the help of others, we were possibly able to contribute to a resolve of the Ruby Eyes.   

Roger Ivester

Be sure to click on the following link for the complete report….

JUNE 2016 OBSERVERS CHALLENGE – M-005

Pencil sketch: 

10-inch reflector @ 208x:   Pencil sketch using a blank 5 x 8 blank notecard with the colors inverted via a scanner.  Note the dark lane on the northern edge, and the chain of stars on the  leading of the SSW  edge of the cluster.  

Scanned Image 161780000

The following image was made using a 4-inch refractor by Dr. James Dire of Hawaii.  Please note the dark lane on the northern edge as shown in the previous pencil sketch.   

M5_4inch

The following Image also by James Dire using a 10-inch reflector….again note the northern dark lane, and the chain of stars extending SSW away from the cluster, as shown in both images.

M5_10inch

 

Roger Ivester:  Observer from North Carolina  

Date: May 27, 2016

M5 – NGC 5904 – Globular cluster in Serpens 
Telescope: 10-inch f/4.5 Reflector and 102mm refractor
Magnification: 208x
FOV: 0.39º NELM: 5.0

Very bright, easily seen through an 8 x 50 finder. At magnitude 5.7, the cluster should be visible naked eye from a dark site. Well concentrated and dense in the central region, with many stars resolved at 208x. When using averted vision, a chain of stars encompasses the northern edge, creating a subtle void between this chain and the main cluster. Also with averted vision, a very faint chain of stars lead off toward the SW. A halo surrounds the main cluster in a mostly circular shape, with many outlier stars embedded in the halo and extending well beyond.

Telescope: 102 mm f/9.8 refractor
Magnification: Eyepiece 26 mm + 2.8x Barlow = 108x

Bright with a well concentrated center and much brighter more intense core. Little to no resolution, however, many brighter outliers are visible. A chain of five stars are easily seen on the north edge of the cluster. The most prominent feature of this cluster, using the 102 mm refractor is the triangular shaped core.  

 

The following write-up/article by Dr. James Dire, which accompanies the two images as posted above. 

M5 is one of the finest globular star clusters north of the celestial equator. Located in Serpens Caput, the cluster is very easy to find. It is 8th degrees due east of 4th magnitude 109 Virginis, 11.5 degrees north of Beta Librae, and 7.5 degrees southwest of Alpha Serpentis. The cluster is a mere 20 arcminutes northwest of 5th magnitude MQ Serpentis (or 5 Serpentis).

M5 was discovered by Godfried Kirch in 1704. Kirch discovered it while looking at a comet nearby. Charles Messier catalog it in 1764. The integrated magnitude of the cluster is 5.6 and its diameter is 28.4 arcminutes. The cluster is an easy find in binoculars!

M5 contains hundreds of thousands of stars. Of those, nearly 100 are known to be RR Lyrae-type variable stars. These variable stars pin down the distance to the cluster at 24,500 light years. The cluster is one of the largest globular clusters in the Milky Way spanning 165 light years. Any object within 200 light years of M5’s center would be gravitationally bound to the cluster, unless moving with a radial velocity equal to the cluster’s escape velocity. M5 is thought to be 13 billion years old, one of the oldest globular clusters known.

Nearby 5 Serpentis is a binary star with components of magnitude 5.0 and 10.1, separated by 11.4 arc seconds. Slightly more than two degrees south of M5 lies another globular cluster known as Polomar 5. Located three times farther away than M5, Polarmar 5 shines at magnitude 11.75 and is 16 arcminutes in size.

I offer two images I took of M5. The first was taken with a 4-inch f/7.9 Stellarvue 102mm APO. The exposure was 30 minutes with an SBIG ST-2000XCM CCD camera. The bright star partial cut off to the lower left of the cluster is MQ Serpentis! The second image was taken with the same camera on a Discovery 10-inch f/6 Newtonian with a Televue Paracorr II coma corrector. The exposure was 60 minutes. The images speak for themselves!  James Dire

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