This image captures numerous small DSOs located in the constellation of Leo Minor at a declination of +35 degrees.  This image is a color-calibrated LRGB image.

The featured galaxy is IC 2497, located 0.7 billion light years away.  This grand design spiral is about 0.5 arc-minute in width, which corresponds to a Milky Way like diameter of 125,000 light years.

Adjacent to the galaxy and at the same distance is the amazing green nebula nicknamed Hanny's Voorwerp.  Only the brightest portion of the voorwerp can be seen in my image.  Overall, it is about the same size as the galaxy. 

This object is one of 20 identified as voorwerp objects.  These are the only DSO objects which have a greenish glow.   My voorwerp galaxy collection is here.  The object here was the first voorwerp discovered in 2007 by Dutch schoolteacher Hanny van Arkel through the online Galaxy Zoo project. This bizarre feature was dubbed Hanny’s Voorwerp (Dutch for Hanny’s object).

The Hubble site describes this phenomenon as follows:  “A quasar beam has caused once-invisible filaments in deep space to glow through a process called photoionisation. Oxygen, helium, nitrogen, sulphur and neon in the filaments absorb light from the quasar and slowly re-emit it over many thousands of years. Their unmistakable emerald hue is caused by ionised oxygen, which glows green. These ghostly structures are so far from the galaxy’s heart that it would have taken light from the quasar tens of thousands of years to reach them and light them up. So, although the quasars themselves have turned off, the green clouds will continue to glow for much longer before they too fade."

The following diagram is from Wikipedia:

Many other small galaxies are also seen the image.  My favorite is the grouping at upper right, highlighted by the superthin spiral LEDA 90934 which is at the same distance away as IC 2497.  This galaxy is about 150,000 light years in diameter.