Messier 28 is a ball of stars (globular cluster) located in the constellation Sagittarius at a distance of 17,900 light years from Earth. Messier 28 contains at least 50,000 stars and is 60 light-years in diameter. Messier 28 was the first globular cluster discovered to contain a millisecond pulsar, a rotating neutron star emitting a beam of electromagnetic radiation with a rotational period between 1 and 10 milliseconds. The pulsar, catalogued as PSR B1821-24, was discovered in 1986 using the Lovell Telescope, a radio telescope at Jodrell Bank Observatory. Charles Messier, the 18th century French astronomer, catalogued over 100 galaxies and clusters. Through the telescopes available at the time, comets, nebulae, globular clusters and galaxies appeared just as faint, diffuse blobs. This image was taken by the NASA/ESA Hubble Space Telescope at visible, infrared and ultraviolet wavelengths.