M97 is one of the few planetary nebulae on Messier's list. It lies just under the 'blade' of he Plough, near the galaxy M108. At its centre is a white dwarf star, the remains of the star that shed the great cloud of dust we now see as the nebula. The two dark patches that give the nebula its name are caused by one of the 'shells' of gas having a hollow a barrel shape.
The photo below replaces the earlier one on this page. This was taken using Hydrogen alpha (Ha - in red) and Oxygen II (Oii in blue-green) filters, hence the relatively faint stars.
M97, the Owl Nebula
Here is Lord Rosse's famous drawing of the Owl Nebula, imaginative but remarkably accurate for a visual observation (it is upside down compared to the above image - there's no 'right way up' in space!) although he moved the central star into an eye socket. One of his clerical friends suggested it looked like 'the visage of a monkey'. Quite an engaging little chap if you ask me.