M93, mag. +6.0, is a bright large open cluster of about 80 stars located in the southern constellation of Puppis. It has an apparent diameter of 22 arc minutes, which is equivalent to about 2/3rds the apparent diameter of the full Moon. Under dark skies, M93 is visible to the naked eye appearing as a misty patch of light. This cluster is an easy binocular object and a wonderful sight in small telescopes where the brightest members form a distinct central triangle. It was one of the last deep sky objects discovered by Charles Messier, which he catalogued on March 20, 1781.
Finding M93 is not difficult. It's positioned in western Puppis a few degrees from the Canis Major border and not far from Sirius (α CMa), the brightest star in the night sky. Sirius can be found by connecting the three bright stars of Orion's belt and extending the line southwards. Positioned 8 degrees southeast of Sirius are Omicron1 CMa (ο1 CMa - mag. +3.9) and Omicron2 CMa (ο2 CMa - mag. +3.0). To locate M93, imagine a line connecting these two stars and then extend it eastwards and slightly southwards for about 10 degrees to reach the cluster.
It's best seen from southern latitudes during the months of December, January and February.
A pair of 7x50 or 10x50 binoculars easily shows M93 with the brightest members resolved. At medium magnifications through small scopes it appears large and quite compact. Towards the centre is an arrowhead or wedge shaped grouping of bright stars. With averted vision the nebulous background resolves into many fainter stars. Larger reflectors of aperture 200mm (8-inch) or greater, reveal dozens of mostly blue giants but also some red giants, which add to the charm of this dazzling cluster.
M93 is 3,600 light-years distant and has a spatial diameter of 20 light-years. It's estimated to be about 100 million years old.
M93 Data Table
|Object Type||Open Cluster|
|RA (J2000)||07h 44m 29s|
|DEC (J2000)||-23d 51m 11s|
|Apparent Size (arc mins)||22 x 22|
|Age (years)||100 Million|
|Number of Stars||80|
|Other Name||Collinder 160|