Barred Spiral Galaxy NGC 4656 & companion NGC 4657

This is a 10 minute exposure with an ST-6 CCD camera thru Kopernik's 20-inch F/8.1 Ritchey Chretien Cassegrain telescope. The field of view is about 5x7 arc minutes.

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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• NGC 4656
• Magnitude: 10.6 (surface brightness = 15th mag)
• Constellation: Canes Venatici
• RA: 12h 43m 57.9s
• Dec: +32d 10' 18" Epoch 2000
• Size (mins): 15.0 x 2.9
• Classification: SB(s)m pec IV
                          Barred Spiral, S-shaped, peculiarities, Luminosity Class IV
  
  

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George Normandin, KAS

June 10th, 1998