M53, mag. +8.0, is a distant globular cluster positioned in the eastern part of the constellation Coma Berenices. Located about 60,000 light-years from the galactic center and 58,000 light-years from Earth, it's one of the outlying globulars of the Milky Way. For comparison, M13 is a mere 25,100 light-years distant.
M53 was discovered by German astronomer Johann Elert Bode on February 3, 1775, who described it as a "rather vivid and of round shape" nebula. The cluster was independently rediscovered by Charles Messier on February 26, 1777. When observing in 1781, he compared it to another recently discovered distant globular M79. As with most globulars, it was William Herschel who first resolved M53 into stars, finding it similar in appearance to M10.
The cluster is quite easy to find, lying just 1 degree northeast of mag. +4.3 star Diadem (α Com). Located 15 degrees directly east of M53 is orange giant star Arcturus (α Boo - mag. -0.05), the fourth brightest star in the night sky. M53 is best seen from northern latitudes during the months of March, April and May.
Through 10x50 binoculars, M53 appears as a very faint speck of light that's slightly fuzzy. An 80mm (3.1-inch) telescope reveals an oval shaped object with a bright centre and extended halo. To begin to resolve member stars, a medium size scope is required. Instruments of 150mm (6-inch) or 200mm (8-inch) apertures will resolve some of the outer stars, especially under dark skies and when using averted vision. The central region appears bright and crisp but unresolved. In total, the outer halo extends for 13 arc minutes, although only about half of this is visible through medium size scopes. Large instruments of aperture 300mm (12-inch) or more resolve the globular well, with stars spread across its full diameter. Considering its vast distance from us the brightness and apparent size of M53 is impressive; it's an intrinsically large globular with a linear diameter of 220 light-years. The cluster contains at least 500,000 stars of which at least 67 are variable stars. It's estimated to be 12.67 billion years old.
Located a degree southeast of M53 is the peculiar globular cluster NGC 5053, a sparse magnitude 10 system containing only 3,500 stars. It appears as a grainy patch of weak light through an 8-inch scope.
M53 Data Table
|Object Type||Globular cluster|
|RA (J2000)||13h 12m 55s|
|DEC (J2000)||18d 10m 08s|
|Apparent Size (arc mins)||13 x 13|
|Number of Stars||>500,000|
|Notable Feature||A number of blue stragglers have been identified in the cluster|