Quote from the Deep Sky Field Guide to Uranometria 2000:
NGC 4657 is a companion superimposed on northeast end of NGC 4656.
According to de Vaucouleurs this is "Probably interacting pair of Magellanic systems". He classifies NGC 4556 as a barred spiral with peculiarities and low luminosity, and NGC 5657 as a low luminosity irregular galaxy. Not surprisingly for an interacting pair, there are several IRAS infrared sources, and X-ray sources, plus a number of point radio sources involved. Based on the published red shift, (Hubble Constant of 62 Km/sec per Mpc) a rough distance estimate is 34 million light years, with a diameter of about 195,000 light years for NGC 4656.
Quote describing NGC 4656 from A.Sandage’s The Hubble Atlas Of Galaxies:
This peculiar irregular is very asymmetric in its surface brightness. The galaxy on one side of the nucleus is bright; on the opposite side, it is very faint. There are two segments on the faint side. The galaxy is well resolved into stars and HII regions.
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George Normandin, KAS
June 10th, 1998