Messier 28

The Globular Star Cluster Messier 28 in the constellation Sagittarius. Credit: Telescope.org The Autonmous Robotic Telescope - COAST Galaxy Camera BVR colour filters

This venerable globular cluster is too far south for me to image successfully from my backyard but I am able to use the Autonomous Robotic Telescope on Mount Teide in the Canary Islands to capture this beautiful grouping of ancient stars.

"M28 is at a distance of about 17,900 light-years away from Earth. It has a combined 551,000 times the mass of the Sun and is 12 billion years old. 18 RR Lyrae type variable stars have been observed in this cluster. In 1986, M28 became the first globular cluster where a millisecond pulsar, PSR B1821–24, was discovered with the Lovell Telescope at Jodrell Bank Observatory. A total of 11 additional millisecond pulsars have since been detected in the cluster with the Green Bank Telescope. As of 2011, this is the third largest known population of pulsars in a cluster following Terzan 5 and 47 Tucanae". : Credit: Wikipedia

Pulsars are the dense remnants of stars that used up their nuclear fuel and consequentially suffered the gravitational collapse of their cores.  A pulsar is a highly magnetized and rotating neutron star or white dwarf that emits a beam of electromagnetic radiation.  As the core spins the beam sweeps across space rather like the light beam from a lighthouse sweeps across the sea. From our perspective here on earth we witness a pulse of radiation evey time the beam is directed towards us. 


The first pulsar was observed on November 28, 1967, by Jocelyn Bell Burnell (now Dame Susan Jocelyn Bell Burnell) and Antony Hewish. For more information follow the links:
https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question45.html