About the Subject

Sh2-129, also known as the "Flying Bat", is an emission nebula in Cepheus, a cloud of glowing, ionized hydrogen gas at distance of roughly 2,300 light-years. In 2011 an amateur astronomer named Nicolas Outters found a very faint area of O III emissions apparently embedded within Sh2-129. It had not been noticed before because of the exceptionally low surface brightness. This very faint bipolar outflow, cataloged as Ou4 and known as the "Squid" nebula, is so faint that with my 12" telescope, each pixel receives only about 19 photons per hour per pixel from the very brightest regions of the squid nebula (4 ADU above background for the brightest regions of the nebula with five minute exposures, 0.33 e-/ADU gain, QE around 85% at O III wavelength). No wonder this object had been previously overlooked. Since 2011 it has become a favorite summertime target for advanced amateur astrophotographers, both because it pushes one's equipment and skills to do the subject justice, and because of the color contrasts and photogenic composition.

Since its discovery, there have been a few attempts to determine whether the Squid Nebula, Ou4, actually resides within the larger Flying Bat, and whether the triple star system HR 8119, which appears to be at the center of OU 4 is, actually, the source.  In 2014, Corradi et al published their findings in Astronomy & Astrophysics, Volume 570. Based on emission-line spatial distribution and kinetic modeling, they determined that Ou4 likely did reside within Sh2-129, and that HR 8119 was the likely source of the outflow. They believe the outflow was launched some 90,000 years ago. While the findings stated that the observed characteristics of the Squid were consistent with a bipolar outflow from HR 8119, they could not rule out other possible unrelated sources.