Markarian’s marvellous chain
A RMENIAN ASTRONOMER BENIAMIN MARKARIAN published a paper in 1961 in which he speculated that eight prominent galaxies in the Virgo Galaxy Cluster are approximately the same distance from us. He showed statistically that the galaxies aren’t a “chance projection” and probably do form a true physical system. Ever since, this eye-catching string of galaxies has been informally known as Markarian’s Chain.
A familiar lament among astronomers is that measuring distances to cosmic sources is exceedingly tricky, even controversial at times. And this is true also for the galaxies in the Chain — 60 years later we’re still not exactly sure how far away they are. Different methods yield different distances, and the more I dug into the professional literature, the more the Chain became a ragged bunch distance-wise. However, recent studies show the estimates converging. We do know, though, that at least seven of the galaxies appear to move coherently through space, and so we’ll take it that Markarian’s Chain does form an actual, curved line of bright galaxies.
The Virgo Cluster is the nearest large aggregation of galaxies and subtends an angle of about 8° across the sky. With somewhere between 1,300 and 2,000 members, it also contains more spiral galaxies than is typical for a cluster this large. The Virgo Cluster has three main concentrations centred on M49, M86 and M87. The latter stole the limelight in 2020 when the Event Horizon Telescope team revealed to the world that they’d imaged the supermassive black
