NGC 4490 + NGC 4485
This image was featured in Universe Today by Tammy Plotner
Discovered by W. Herschel on 14th of Jan 1788 in the constellation of Canes Venatices this pair of galaxies are interacting in a gravitational way. Originally spiral shaped both partners pertubate their physical appearence dramatcially so the original spiral structure can only be guessed in the smaller NGC 4485 which as a consequence of the gravitational influence over the past million years has lost it's spiral structure and is now categorized as an irregular shaped galaxy.
Being 10m2 bright, NGC 4490 measures 10.6 by 3.2 arc minutes, while NGC 4485 shines at 12m3 and holds only 2.4 by 1.8 arc minutes. Located some 26 Mio LY away from Earth both galaxies move away from each other being separated by some 25000 Lightyears at this time.
Whenever galaxies collide or in this case, gravitationally interfer with each other, Hydrogen gas masses are being shared and merged, causing star forming/burst regions. One of these larger star forming areas that measure around 1 Mio solar masses can be found in the south-east tail of of NGC 4490 being approximalty 200 Mio years old. Further star burst regions are visible in this image inbetween the two galaxies.
Most recently a Supernova took place in that galaxy: SN 2008 ax. It was first discovered by a Japanese Amateur Astronomer! Rick Johnson imaged the SN with his 14" LX200R, L=4x10', RGB=1x10', STL-11000XM, Paramount ME. SN 2008 AX was visible for about 3 to 6 months - depending on the scope you used...(-: Torsten Grossmann imaged the galaxies again in early 2010 and we could no longer find any hint of the SN - which of course was to be expected. Nevertheless, within NGC4490 a remnant of that star that has gone supernova is still present and renders potential material for new stars that are yet to come.