Trio in Virgo

Three galaxies in Virgo, close enough to be pulling on one another and to have left the evidence: faint bridges of material stretched between them. Halton Arp listed the group in his 1966 Atlas of Peculiar Galaxies as Arp 286; it is also known as the NGC 5566 group.

Three galaxies and the bridges between them

The large spiral at the centre is NGC 5566, about 150,000 light-years across — larger than the Milky Way, and the dominant member of the group by a wide margin. Above and to its left is NGC 5569, a small blue spiral. To the right is NGC 5560, visibly bent out of shape. What connects them is not a trick of alignment: the material drawn out between the three is real, pulled from their discs by the encounter.

Which galaxy is pulling on which

NGC 5560 is the one that has taken the damage, and the mass responsible is NGC 5566. That distinction matters, because the small blue spiral sitting nearby looks like the obvious culprit and is not: NGC 5569 does not have anything like the mass required to warp a disc that size. The distortion runs the other way round, from the big spiral to the small distorted one, with NGC 5569 caught in the same field.

Five hours, and an APOD

This image is 5.3 hours of LRGB — the shortest integration of any page on this site, by a long way — and it was selected by NASA as the Astronomy Picture of the Day on 10 June 2022. That is worth saying plainly, because the assumption usually runs the other way. Depth is not what decided this frame. The data is clean, gathered under a Chilean sky, and it holds together at five hours what a noisier set would still be fighting at fifty. Everything after that was processing.