The “Markov 1” Asterism in Hercules
By Paul Markov

Update - July 2003: The "Markov 1" asterism (pictured below) is included in the book "Star Clusters" by Archinal and Hynes on page 145.

Reading “The Mackie 1 Asterism” article in the April issue of The Journal renewed my interest in an observation I had made on July 4, 2000. On that night I was star hopping to the DoDz open clusters in Hercules and while on my way to DoDz 9 I passed by the star Xi Hercules (also known as 92 Hercules). Just north of this third magnitude star I noticed a very small grouping of stars that stood out very well in a shape very similar to that of the “teapot” asterism of Sagittarius. Because it was not labeled as a cluster in any of my star charts, I moved on to the much less impressive DoDz open clusters and promptly forgot about it.

Photo Credits: The Digitized Sky Survey copyright 1994, Association of Universities for Research in Astronomy, Inc. http://stdatu.stsci.edu/dss/index.html

After reading Guy Mackie’s article I thought I should revisit this star grouping and see if anyone knew more about it. I too contacted Dr. Brent Archinal (formerly of the U.S. Naval Observatory), an expert on open star clusters. Dr. Archinal confirmed that this grouping did not have a designation on any of his atlases or catalogues and suggested I try to determine whether this was a physical cluster by analyzing the proper motions and V and B magnitudes for each of the component stars. I followed his advice and found that the proper motions of the nine brightest stars in the grouping are all very different; this indicated that each star is traveling in a different direction, implying it could not have been a physical cluster. Dr. Archinal agreed with my cursory analysis, however he warned me that the available data (from the Tycho-2 star catalogue) may not be all that accurate and that the error margin of the proper motions could be very large, adding uncertainty to my conclusion. He also noted that there does not seem to be a pattern for the V and B magnitudes, and because this grouping is quite far away from the plane of the Milky Way, the possibility of it being a physical cluster are reduced.

Whatever its real nature, this grouping is a very interesting telescopic target and makes for a good asterism, at the very least. Dr. Archinal suggested the asterism be named “Markov 1” or “Markov J1757.2+2929”, as per the International Astronomical Union’s nomenclature guide lines, and also expressed an interest in including Markov 1 in an upcoming book he is co-authoring (with Steve Hynes of the U.K.) called “Star Clusters”.

“Markov 1” is located at Right Ascension 17 hrs 57 min, Declination +29 deg 29 min, it is comprised of nine brighter stars ranging from magnitude 8 to 10, its size is approximately 15 arc-minutes, and is easily visible with a small telescope even from light polluted skies. The asterism, which is just 0.25-degrees north-west of Xi (92) Hercules, a magnitude 3.7 star, shows ups well on both the Digitized Sky Survey image (Figure 1) and Uranometria 2000.0 (star chart 116) and can be observed during most of the year, except Winter.

Copyright (C) 2001 by Paul Markov


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