M81 (Bode's Galaxy) and M82 (The Cigar Galaxy)

Constellation: Ursa Major

Distance: 12 million light years

Two galaxies locked in a gravitational struggle for the past billion years or so, the last close encounter occurring about 20 million years ago.

M81, the grand spiral galaxy on the left, was discovered by Johann Elert Bode in 1774 and still bears his name. Its active galactic nucleus contains a supermassive black hole. The faint blue dwarf galaxy just above M81 in this image is designated Homberg IX, one of several dwarf galaxies adjacent to M81 likely formed recently from condensing debris from the interacting galaxies.

The most recent close violent gravitational encounter likely resulted in distortion of M82 (also known as the Cigar Galaxy) on the right, and stimulated a burst of star formation. M82 shows a rate of star formation ten times greater than our own Milky Way.

Careful examination of the image shows heterogeneity of the background sky caused by the "integrated flux nebula (IFN)". This can be better seen in the grayscale version below. These nebulous clouds are not associated with M81 and M82 but rather lie just beyond our own galaxy. Unlike classic emission or reflection nebulae that are illuminated by specific stars, the IFN is illuminated by the energy of the integrated flux of all of the stars in the Milky Way.