Ou-4 Bipolar Nebula

Ou-4 is a faint, bipolar nebula discovered by French amateur astronomer Nicolas Outters in 2011. Its full length covers 1.2 degrees in the sky and is thus about 2.5 times longer than shown in the above high-resolution image that shows the central part. It is located within the HII region of Sharpless2-129 in Cepheus at a distance of 2,300 light years. At that distance, it is determined to be 50 light years across. It is referred to as the Giant Squid Nebula or the Flying Bat Nebula, which is better defined in wide-field images. Its bipolar tubular structure is similar to planetary nebula KjPn 8 which I’ve previously imaged here. It is thought that this bipolar structure came from the outflow ejected from one of the stars in a multiple-star system about 90,000 years ago. Ou-4 is primarily defined by its OIII emission at optical wavelengths as a blue-green color in the above image. The reddish background color comes from H-a emission of Sh-129. These nebular and background details in this 42 hour image came from using 3 nm OIII and H-a filters color-mapped as described above to provide natural color. 3 hours of RGB data were added for star colors. This is a collaboration with Josep Drudis.