July 2019 - Picture of the Month
Messier 55 in Sagittarius
Nebulosity has dominated this column (and many would say why not?), but I like to bring a little variety and I felt it was time for a change. I was also shocked to discover that I've only featured Sagittarius once in Picture of the Month.
Something from this imposing constellation was in order and I wanted a cluster this time. So I give you a globular cluster that certainly fits the bill with thanks to Bernhard Hubl.
Messier 55 is large and bright, but also loose down to its core with a Shapley–Sawyer Concentration Class of XI. At about 5400 parsecs distant it's about 100 light-years across and contains 269,000 solar masses. It seems that it has a population of blue stragglers near the core.
Considering it's 6.3V magnitude and being 19 arc-minutes in diameter M55 isn't too hard to spot in binoculars. A small telescope will resolve plenty of stars in this open globular cluster. It might be a bit tricky for those of us at northern latitudes, a good southern horizon helps, but well worth a look as the nights grow longer.
James Whinfrey - Website Administrator.