NGC 4889 is a supergiant elliptical galaxy in the constellation of Coma Berenices. It's one of the principal members of the Coma Cluster, a large cluster of a least 1,000 galaxies located 335 million light-years distant. This group of galaxies is comparable to the Virgo Cluster but six times further away.
NGC 4889 lies at the centre of the Coma Cluster, a region it dominates along with another supergiant elliptical, NGC 4874. The Coma Cluster is also known as Abell 1656 and together with the Leo Cluster (Abell 1367) they are the major constituents of the Coma Supercluster. With an apparent mag. of +11.5, NGC 4889 is the brightest Coma cluster member and can be glimpsed with just a 100mm (4-inch) refractor, which is remarkable considering how far away it is.
Many amateur astronomers like to push telescopes to test their deep space distance records. The obvious starting point is the Messier catalogue and the most distant Messier galaxy is M109, at 83.5 Million light-years. To go deeper still you need to search elsewhere and the Caldwell catalogue has a few good examples. One of them is NGC 4889 and it's one of the most distant galaxies easily visible with backyard scopes. The current estimate has it at 308 Million light-years.
NGC 4889 is positioned about 2.5 degrees almost due west of beta Com (β Com - mag. +4.3). A small 100mm (4-inch) scope shows a faint out of focus "star", somewhat similar in appearance to a planetary nebula. Given its great distance from us, it's no surprise that this galaxy appears faint and small. In total, it spans 2.8 x 2.0 arc minutes but visually appears about half the size. Although it appears unimpressive, this is only due to its great distance, which masks the true spectacular nature of this object. In reality, this super galaxy is enormous with an actual diameter of 250,000 light-years. Also faintly visible with small scopes about 7 arc minutes east of NGC 4489, is its slightly fainter twin galaxy, NGC 4874.
To really appreciate this region of sky a large scope is required. With a 450mm (18-inch) Dobsonian, NGC 4889 and NGC 4874 are clearly visible and appear slightly oval shaped. The extra aperture afforded by such instruments reveals hundreds of fainter galaxies belonging to the Coma Cluster. Most are 15th magnitude or fainter and are scattered about 3 degrees centred on NGC 4889.
NGC 4889 was discovered by William Herschel on April 11, 1785. It's best seen from northern latitudes during the months of March, April and May.
NGC 4889 Data Table
|Object Type||Elliptical Galaxy|
|Classification||cD; E4; Db|
|Distance (light-years)||308 Million|
|RA (J2000)||13h 00m 08s|
|DEC (J2000)||+27d 58m 37s|
|Apparent Size (arc mins)||2.8 x 2.0|
|Number of Stars||5 Trillion|
|Notable Feature||Massive galaxy and principal member of the Coma Cluster|