This is the classic Owl Nebula, a planetary nebula located 2000 light years away in the constellation of Ursa Major at a declination of +55 degrees. This magnitude 9.8 nebula, also known as NGC 3587, is believed to be about 8000 years old. My image shows that the primary gas in this nebula is oxygen, shown in blue, with some outer rim red highlights which are due to hydrogen.
The nebula is just larger than 3 arc-minutes in apparent size, with an actual diameter of almost 2 light years. This is fairly typical - many of the 210 PN I have imaged have been around 2 light years in diameter.
Although the nebula was discovered by French astronomer Pierre Méchain in 1781, the Owl nickname supposedly comes from a drawing of the nebula by William Parsons, 3rd Earl of Rosse, in 1848. But
his drawing looks nothing like an owl to me.
Whatever the origin of the nickname, the structure of the nebula is fascinating. An outer faint unsymmetric halo of oxygen is barely visible and was not detected until 1991. The bright inner nebula takes on a 3-D appearance if looked at long enough, with many darker void areas visible. The primary inner structure is a roughly hourglass shaped void area which could have been formed by bi-polar outflow from the visible central bluish 14th magnitude source star. We are viewing this shape not face-on but at an oblique angle, which makes the shape harder to recognize and resolve.
The structure of this nebula is not unique. My poster of Owl-type nebulae is
here.
Comments