This object captures a pair of emission nebulae -- Sh2-129 (The Flying Bat Nebula) shown in the red ionized hydrogen emissions, and the very faint OU-4 (The Giant Squid Nebula) shown in the cyan ionized oxygen emissions. These objects are 2300 light years away in the constellation of Cepheus at a declination of +60 degrees.

OU-4 was recently discovered in 2011. It is very faint but very large in the sky, spanning the equivalent of 2 full moons. This nebula is estimated to be 100,000 years old based upon its outflow and size. It is about 50 light years long.

The structure and size of OU-4 is unusual. Although we do not know its exact origin, it seems logical that it has formed from ionized oxygen emissions emanating from the bright triple star system (HR 8119) which it is centered upon. One possibility is that the outflow is produced from an eruptive outburst caused by mass accretion in a binary system. This event is called an intermediate–luminosity optical transient (ILOT).

So, is this a planetary nebula? Some people, dating back many years, consider PN to simply be gas ejected from a star, which this is. But a PN is now defined as a shell of ionized gas ejected from a red giant star late in its life. The shell mechanism seems more complicated than that here. More importantly, the typical size of a PN is about 1 to 3 light years or less. This one extends 50 light years. My belief is that this is not a PN, but I will leave that debate to the scientists.

I like the complex multi-polar structure of this nebula. Bow shocks are seen in multiple places, particularly the bright arc at the bottom of the nebula. The radius of all of these bowshocks point back to the triple star system. The nebula looks to be a continuous surface bubble except in two spots about 1/4 of the way up from the bottom of the nebula, where the outflow appears to have broken through the bubble.

This nebula is very similar in shape to KjPn 8, which is also large in size and believed to be caused by an ILOT. Interestingly, that nebula is hydrogen, not oxygen like this one.