NGC 4449

NGC 4449 is a dwarf galaxy located in Canes Venatici, 20,000 light years across and c12.5 million light years from Earth. Its structure is similar to the Large Magellanic Cloud (LMC), the satellite galaxy to our Milky Way.  Evidence for a very high rate of star formation is indicated by the presence of many young blue stars and pinkish star forming regions.

It was the first dwarf galaxy to have an associated tidal stream identified which is the product of violent interactions with another satellite dwarf galaxy, NGC 4449B. The faint remnants of NGC4449B appear as a dim trail of stars and dust which will eventually merge with NGC 4449.

The observable mass of NGC 4449 is insufficient to explain the interactions with other objects and so the missing mass is called dark matter.  Dark matter is believed to surround all galaxies, including our own. Dwarf galaxies have higher proportions of dark to normal matter and so what appears as a minor amount of observable stellar matter interacting with NGC 4449 may actually represent a large amount of dark matter, which may explain the very high rate of star formation.  

The LRGB image below was taken by my Esprit 150 and represents just over 15 hours integration time.