Johannesburg Centre, Astronomical Society of Southern Africa


A Cluster Hop Around The Body of the Scorpion

As the scorpion proudly guards our view of the centre of the Milky Way Galaxy, and crawls serenely over our winter sky zenith, spend a leisurely half-hour globular and cluster-hopping around its heart, body and sting territory.

First stop ? Antares, slip due west 1.5 degrees to the bright globular cluster M4 (NGC 6121). A loosely packed cluster with a central bar-like concentration of stars running approximately north-south along the cluster. Mag 5.9 at 6800 light years.

M80 (NGC 6093) is a rather faint, very compact globular cluster approximately half-way between Antares and beta Scorpii (4 degrees NNW of Antares). Mag 7.2 at 27000 light years.

M62 (NGC 6266) is usually listed in Ophiuchus but its close proximity to the stinging constellation makes the scorpion?s influence on it irresistible. At Mag 6.6, it is small (14 arc seconds), compact and quite luminous. To find it, form an east-facing equilateral triangle with Tao and Epsilon Scorpii.

Move to Zeta Scorpii and change to your lowest magnification eyepiece. Notice the wide double of Zeta Scorpii at mag 3.6 and 4.7. A nudge half a degree north lies the open cluster of NGC 6234 and the loose grouping of Trumpler 24. I have dubbed this the guitar cluster as the entire grouping forms the outline of an acoustic guitar. You can even notice the strings and tiny fret markings on the guitar. A stunning cluster in low magnification or even binoculars.

Moving on to the scorpion?s tail area, M6 (NGC 6405) is also known as the Butterfly Cluster. This is a beautiful open cluster, with BM Scorpii as the brightest member - a sixth magnitude yellow giant. Look for the 7-star ?kappetjie? formation punctuating BM Scorpii. This forms the antennae of the butterfly. Trace the open wings of the butterfly as the brightest members glisten like twinkling diamonds. The cluster comprises about 80 stars in the vicinity of 1900 light years.

A slight nudge south-east of M6 exposes the magnificent open cluster of M7 (NGC 6475). Best in low magnification, this cluster lies about four degrees NNE of Lambda Scorpii at 782 light years (collectively at Mag 3.3). It is extremely large at nearly two full moon diameters. The cluster also numbers about 80 stars, the brightest of which range from mag 5.6 to 9.0. I could also resolve several close visual binaries in the cluster.

And now for the stunner! There is a star designated as G Scorpii, which forms an east-facing equilateral triangle with Lambda Scorpii and Iota 1 & 2 Scorpii as the base. Globular Cluster NGC 6441 nestles a mere 90 arc seconds east of G Scorpii. It is small, very dense and extremely compact. Mag 7.2 at 33500 light years.

Finally, globular cluster NGC 6388 lies about 2 degrees south of Theta Scorpii. At Mag 6.8, I found it remarkably similar in size, structure and concentration to NGC 6093.

Shortly after that final catch, the scorpion burrowed itself in dusty cloud and disappeared from sight. A joyous half-hour of manual search and recovery!

All observations with a 10? SCT, 25mm super Plössel, 32mm super wide from 20:30 to 21:00 SAST on 15 July 2001.

Dave Gordon


Hits since October 2003: Hit Counter  

Neither ASSA nor the Johannesburg Centre is responsible for the content of any site to which this web presence might be linked. The opinions expressed by our contributors are not necessarily those of the Society. No responsibility is assumed for the accuracy of information presented on this site, nor for its use or the consequences thereof.

Comments & Suggestions? Mail to webmaster@assajhb.co.za