There’s nothing particularly “new” in the sky this week.  No events with critical timing, no new comets or other discoveries (although there is apparently a new Supernova in the Pinwheel Galaxy…)

So, I got a little adventurous with the camera, and pulled out the telescope for followup.  The prey – Globular Clusters!

I’ve talked some about open clusters (Pleiades, Hyades, Coma Berenices, the Beehive…), but Globs are different.  Relics of an ancient past, globulars lie outside the galaxy, in a roughly spherical pattern like some sort of gigantic Oort Cloud on a galactic scale.  Rather than being a scattered collection of a few hundred stars, the globulars are densely packed, roughly spherical collections of up to a million or more.  They are believed to be relics of our galaxy’s birth – leftovers from a day when our galaxy was an irregular cloud of dust and star-producing regions.  As angular momentum in that cloud increased, much of the material spun in, and was flattened into the galactic disk.  The stars on the periphery missed the memo, and stayed put, instead clumping toward each other.  The stars in these clusters are truly ancient – 10 billion years, or more, old.

Bootes-Hercules, StellariumLast night was my first try, so I went hunting for the brightest globular in the northern sky, Messier 13, the Great Cluster of Hercules.  Hercules, like so many other constellations representing people, is essentially a trapezoid, called “The Keystone” in Hercules’ case, with arms and legs – and this arrangement looks particularly ready for action!  The Stellarium screenshot here shows its position, facing east.  It’s just below (east) of Bootes (which we’ve talked about a lot!) and the semi-circle of Corona Borealis.  M13 is halfway between the bright stars Arcturus and Vega, about a hand-width below comet Johnson.

Unlike Johnson, M13 is faintly visible to the naked eye, though that’s only true on a really dark night.  Last night I was trying to spot it through scattered clouds, and the light pollution and reflections of ground light off the clouds made it impossible to see without binoculars.  I took a wide-field DSLR shot which gives you a good impression of the binocular view.  The stars at the bottom of this shot, just above the cloud, form the top of Hercules’s Keystone, and M13 is about a third of the way along this line from left to right.  It almost looks like a tailless, compact comet.  There’s something distinctly un-star-like about this object.

Great Cluster Hercules, M13.jpgNow, I’m not set up for photography through my telescope, but pulling out the 6″ reflector, I was able to achieve something like the below (courtesy NASA).  You can’t see each of the 300,000 or so stars, but WOW.  My 6″ couldn’t quite achieve this degree of resolution, but the effect was similar.


It’s hard to imagine being the first to have taken some magnification to that fuzzy spot in Hercules and to have realized what it was.  Edmund Halley is credited with that feat in 1714, solving the mystery of why this “comet” never moved.  Today, we can see much more, of course.  I’ll leave you with a shot of M13’s core, taken by Hubble.

Hope you enjoyed this little foray into reachable deep-sky objects.  We will soon have evening views of the Milky Way’s core, and there are many targets such as this to pursue, even with a small telescope!

Get Out There!



Core of Messier 13, the Great Cluster of Hercules, via Hubble (NASA – public domain)

2 thoughts on “Astronomy: Week of 5/21/17 (Globs!)

  1. If I remember correctly, the Hercules Cluster was one of the first things I went looking for, way back when I started dabbling in astronomy. I’d read somewhere that it was a good target for beginners. It took awhile, but I remember being able to see it (barely) with a pair of binoculars.

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