Ou4: The Giant Squid Nebula

Explanation: A mysterious squid-like cosmic cloud, this nebula is very faint, but also very large in planet Earth's sky. In the image, composed with 30 hours of narrowband image data, it spans nearly three full moons toward the royal constellation Cepheus. Discovered in 2011 by French astro-imager Nicolas Outters, the Squid Nebula's bipolar shape is distinguished here by the telltale blue-green emission from doubly ionized oxygen atoms. Though apparently surrounded by the reddish hydrogen emission region Sh2-129, the true distance and nature of the Squid Nebula have been difficult to determine. Still, a more recent investigation suggests Ou4 really does lie within Sh2-129 some 2,300 light-years away. Consistent with that scenario, the cosmic squid would represent a spectacular outflow of material driven by a triple system of hot, massive stars, cataloged as HR8119, seen near the center of the nebula. If so, this truly giant squid nebula would physically be over 50 light-years across.

Page 2

There are strange rings. The rings are probably 3D shells, but how they were made remains a topic of research. They were created in a system that is 6,000 light years away from the constellation of the Swan. Wolf-Rayet stars are large and bright. Heavy elements such as carbon are created and dispersed by them. The other star isn't as active as the other one. The two stars approach each other about eight times a decade. The X-ray emission from the system increases when it's closest to the ground. More details and more dust shells can be seen in the featured IR image by the new space telescope.