NGC 1851 is a globular cluster in the southern constellation of Columba that's easily visible with binoculars. It's an unusual cluster since it was probably a former member of the Canis Major Dwarf galaxy. This dwarf galaxy and Local Group member was discovered in 2003.
James Dunlop, a Scottish astronomer based in Australia, discovered NGC 1851 on May 29, 1826. It shines at mag. +7.3 and spans 11 arc minutes of sky, making it the brightest and largest deep sky object in Columba.
The globular is best seen during the months of December, January and February. From northern temperate locations it appears low down, apart from latitudes above 50N where it's not even visible at all. The object is number 73 in the Caldwell catalogue.
Columba is not a difficult constellation to recognise under a dark sky. Its brightest stars shining at third magnitude. To locate NGC 1851, look towards the southwestern corner of the constellation, 9 degrees southwest of Phact (α Col - mag. +2.7). In this barren region of sky you will find NGC 1851.
Through popular 7x50 or 10x50 binoculars, the globular appears as a small fuzzy ball of light. With an 80mm (3.1-inch) scope at low magnifications it's unresolved, spans about 5 arc minutes and looks somewhat like the halo of a comet. The brightest individual members are of 13th magnitude and a 200mm (8-inch) scope will resolve some of them, especially under dark skies. NGC 1851 is a superb site when seen through large backyard scopes. A 300mm (12-inch) instrument reveals a large, bright round ball of stars that's well resolved at 250x magnification. There are several chains of stars visible that branch outwards from the centre.
NGC 1851 is 39,500 light-years distant. It has an actual diameter of 130 light-years and is estimated to contain 200,000 stars. The cluster is 9.2 billion years old.
NGC 1851 Data Table
|Object Type||Globular Cluster|
|RA (J2000)||05h 14m 06s|
|DEC (J2000)||-40d 02m 50s|
|Apparent Size (arc mins)||11|
|Age (years)||9.2 Billion|
|Number of Stars||200,000|