<p><b>Messier 28</b>
</p><p>M28 is a globular cluster located 17,900 light-years away from Earth in the constellation Sagittarius. It was discovered by Charles Messier in 1764. With an apparent magnitude of 7.7, the cluster appears as a faint patch of light through a pair of binoculars. Large telescopes can resolve its individual stars more effectively. The month of August is the best time to view M28.
</p><p>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.
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This Hubble image of M28’s center was assembled from observations taken at visible, infrared and ultraviolet wavelengths.
Credits: NASA, ESA, STScI, R. Buonanno (Universita di Roma Tor Vergata), K. Gebhardt (University of Texas at Austin), J. Grindlay (Harvard University), and F. Ferraro (Universita di Bologna)
<a rel="nofollow" class="external free" href="https://www.nasa.gov/feature/goddard/2017/messier-28">https://www.nasa.gov/feature/goddard/2017/messier-28</a>