NGC 3521 is around 26 million lightyears away, and a distant member of the Local Group, of which our galaxy is a part. It is located in the very south of the constellation of Leo.
The galaxy is embedded in a halo, which contains the remains of smaller satellite galaxies, that have been ripped apart by tidal forces. However, this is not a rapid process, taking multiple passes of the larger galaxy and a gradual loss of cohesion. It may take hundreds of milions, if not billions of years for the larger satellite galaxies.
There is evidence from 'galactic archaeology' that our own galaxy has cannibalised around 15 small galaxies, each with at least 10 million solar masses. It is thought that most of the stars in the halo of our galaxy, come from these mergers.
This LRGB image is the result of 1h 35m of data capture, remotely imaged from Spain in February 2021, with an SBIG STL-6303 camera through a 12.5-inch Planewave CDK reflector.
Photographer: Graham Wilcock