M28 – Globular Cluster

M28 is a globular cluster located 17,900 light-years away from Earth in the constellation Sagittarius. It was discovered by French astronomer Charles Messier in 1764. The cluster appears as a faint patch of light through a pair of binoculars. The month of August is the best time to view M28 and its roughly 50,000 stars. The cluster is most notable for being the first of its kind known to contain a millisecond pulsar: PSR B1821–24. This dense neutron star rotates rapidly (about once every three milliseconds) and emits radiation from its poles, which sweeps past Earth as the star spins, much like a beam of light from a lighthouse. This makes it appear to be pulsing to observers on Earth. PSR B1821–24 was discovered in 1986 using a radio telescope in England called the Lovell Telescope.