Messier 60, NGC 4649

Messier 60 (also known as NGC 4303) is a giant elliptical galaxy in Virgo, and has a nearby spiral companion (NGC 4649) with which it appears to be interacting.

Messier 60 and Messier 59 were both discovered by Johann Gottfried Koehler in April 1779, during observations of a comet in the same part of the sky. Charles Messier listed both in the Messier Catalogue four days after Koehler's discovery. M 60 was also independently found by Barnabus Oriani, who missed M 59, one day after Koehler.

Observing Messier 60

M 60 is the easternmost in a row of three galaxies (M 58, M 59, and M 60) in this region of the sky. At lower magnifications, it lies in the same low-power field of view as M 59, which is 25' away. M 60's visual magnitude of 8.8 makes it the third-brightest giant elliptical galaxy in the Virgo cluster. It has a large 7' x 6' disk; amateur telescopes, however, only show its bright 4' x 3' central region.

The nearby fainter spiral NGC 4647 is conspicuous in telescopes starting from 4" aperture; the halos of the two galaxies appear to touch. For this peculiar property, Halton Arp listed M 60 as no. 116 in his Catalogue of Peculiar Galaxies, with the description "Elliptical Close To and Perturbing a Spiral".

A type Ia supernova (SN 2004W) was observed in M 60 in 2004.

Physical Properties

M 60 is one of the giant elliptical galaxies at the core of the Coma-Virgo Supercluster. At a distance of 65 million light years, it has a diameter of over 140,000 light years, an absolute magnitude of -22.3, and a luminosity of 100 billion suns. It has a mass close to a trillion suns, and is one of the largest elliptical galaxies known.

The Hubble Space telescope has investigated M 60's core and found evidence that it contains a massive central object of about 2 billion solar masses. Photographs obtained with larger instruments show a large system of about 5100 faint globular clusters in M 60's halo.

NGC 4647 appears approximately 2.5' away from Messier 60; the optical disks of the two galaxies overlap. Although this suggests that the galaxies are interacting, photographic images of the two galaxies do not reveal any evidence for gravitational interactions between the two galaxies, as would be suggested if the two galaxies were physically close to each other. This suggests that the galaxies are at different distances, and are only interacting weakly if at all.