Highly bipolar-collimated outflow Ou4 nebula. Shown here is the whole mosaic as obtained using the Isaac Newton Telescope, where red is Hα+[NII], green is [OIII], and blue is the Sloan g broadband filter. Note that the outflow, also nicknamed "the Giant Squid", has an extension of 2.5 full moons on the sky. Credits: Romano Corradi (IAC), Nicolas Grosso, Agnès Acker, Robert Greimel, Patrick Guillout. Image processing by Gabriel Pérez (IAC) [ JPEG | TIFF ].

Ou4 is a recently discovered bipolar outflow with a projected size of more than one degree in the plane of the sky. It is apparently centred on a young stellar cluster — whose most massive representative is the triple system HR 8119 — inside the HII region Sh 2-129. The apparent position of Ou4 and the properties deduced in this study are consistent with the hypothesis that Ou4 is located inside the Sh 2-129 HII region, suggesting that it was launched some 90,000 yrs ago by HR 8119.


More information:

• NASA's Astronomy Picture of the Day, 17th July 2014.
• A. Acker et al., 2012, "Discovery of New Faint Northern Galactic Planetary Nebulae", RMXAA, 48, 223. Paper.
• R. L. M. Corradi et al., 2014, "Gas physical conditions and kinematics of the giant outflow Ou4", hal-01022286. Paper.