Arp 242 - NGC4676A and B - the Mice Galaxies are a pair of colliding spiral galaxies pulling each other apart in the constellation of Coma Berenices, 290 million light-years from Earth. They were discovered by William Hershel on March 13, 1785 and are nicknamed “the Mice” because of their long trails of stars and gas emanating from each galaxy. The relative difference between gravitational pulls on the near and far sides of each galaxy produces the tails, as well as a bridge of stars between the two, with the tail of the rightmost galaxy seen edge-on and appearing thin. Each spiral galaxy has likely already passed through the other and will do so repeatably over hundreds of millions of years until coalescing into a single larger galaxy.
- Right Ascension: 12h 46m 10s, Declination: +30d 37m 12s (Epoch 2000)
- Constellation: Coma Berenices
- Distance: 290 Mly
- Apparent Magnitude: 14.7 / 14.4
- Apparent size: NGC4676A: 2.3 x 0.7 arc-min, NGC4676B: 2.2 x 0.8 arc-min
- Exposure Interval: April thru June, 2015
- Exposure: Lum: 4.7 hrs, Red: 3.7 hrs, Green: 3.3 hrs, Blue: 5.3 hrs (total 17 hrs)
- Instrument: RCOS 20 inch @ f/8.2 (fl-4116 mm), SBIG ST8-XME (1 pixel = 0.4509 arc-sec)
- Processing: PixInsight