Object Name: Messier 85
Alternative Designations: M85, NGC 4382
Object Type: SO Spiral Galaxy
Constellation: Coma Berenices
Right Ascension: 12 : 25.4 (h:m)
Declination: +18 : 11 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 9.1 (mag)
Apparent Dimension: 7.1×5.2 (arc min)
Locating Messier 84: Messier 84 is located on the northern boundary of the Virgo Cluster of galaxies about halfway between Epsilon Virginis and Beta Leonis. It is considered either a lenticular spiral seen face-on – although it looks elliptical, and it will show as its bright core and round form for a larger telescope and a small round smudge for smaller ones. It requires dark sky and a telescope to be seen.
What You Are Looking At: Somewhere in this huge conglomeration of globular clusters and older yellow stars, there’s a bright mystery. A transient phenomena…
According to S. R. Kulkarni (et al): “Historically, variable and transient sources have both surprised astronomers and provided new views of the heavens. Here we report the discovery of an optical transient in the outskirts of the lenticular galaxy Messier 85 in the Virgo cluster. With a peak absolute R magnitude of -12, this event is distinctly brighter than novae, but fainter than type Ia supernovae (which are expected in a population of old stars in lenticular galaxies). Archival images of the field do not show a luminous star at that position with an upper limit in the g filter of about -4.1 mag, so it is unlikely to be a giant eruption from a luminous blue variable star.”
While it would be wonderful to believe the line of sight star we see when we look at M85 is the culprit, it just isn’t so. “Over a two-month period, the transient source emitted radiation energy of almost 1047 erg and subsequently faded in the optical sky. It is similar to, but six times more luminous at peak than, an enigmatic transient in the galaxy M31.” continues Kulkarni; “A possible origin of M85 OT2006-1 is a stellar merger. If so, searches for similar events in nearby galaxies will not only allow study of the physics of hyper-Eddington sources, but also probe an important phase in the evolution of stellar binary systems.”
But there’s more than that going on! Let’s take a look at another luminous source found this time in the infrared…. “M85 OT2006-1 is the latest and most brilliant addition to the small group of known luminous red novae (LRNe). An identifying characteristic of the previously detected events (M31 RV, V4332 Sgr, and V838 Mon) was a spectral redward evolution connected with an emerging infrared component following the optical decay.” says A. Rau (et al), “Here we report on the discovery of a similar feature in Keck NIRC and Spitzer photometry of M85 OT2006-1 6 months posteruption.”
History: M85 was discovered on March 4, 1781 by Pierre Mechain. When he turned his reports over to Charles Messier to confirm, Messier took a closer look at the whole area and on March 18, 1781, he cataloged it as M85, together with seven own discoveries of member galaxies of the Virgo Cluster, and globular cluster M92. Said Messier: “Nebula without star, above and near to the ear of the Virgin [Virgo], between the two stars in Coma Berenices, No.s 11 and 14 of the Catalog of Flamsteed: this nebula is very faint. M. Mechain had determined its position on March 4, 1781.”
Three years later it was observed by Sir William Herchel – who though he’d resolved it! “Two resolvable nebulae; the precedint [Western] is the largest, and with 157 seems to have another small nebula joined to it, but with 240 it appears to be a star. The following nebula is II.55 [NGC 4394].” Although he really didn’t resolve the galaxy, at least he noted the foreground star!
Top M85 image credit, Palomar Observatory courtesy of Caltech, M85 2Mass Image, M85 Spitzer image and M85 color image courtesy of NOAO/AURA/NSF.