Hover your mouse over each blue dot for the name of the object, or click on the dot for a detail page. This map was created using the all-sky hydrogen-alpha map produced by Douglas Finkbeiner from data collected by the WHAM, VTSS and SHASSA hydrogen-alpha surveys.
The enormous HII region Sh 2-310 is ionised by two multiple star systems (Tau Canis Majoris and UW Canis Majoris) each made up of several O-class stars. Sh 2-310 is located at a distance of 1500 parsecs and with a diameter of more than 200 parsecs, is one of the largest known HII regions in the Milky Way.
Despite its prominence, this nebula does not have a common name. Perhaps this could be the Dog Arch, given its arch-like shape and its location in the direction of the constellation Canis Majoris.