Coming out of its shell

Nicolas Martino/Yann Sainty/Team StDr, taken in France

The faint oxygen universe continues to reveal itself as amateurs go ever deeper with narrowband Oxygen-III (OIII) filters. The latest find comes from a team that includes the trio who discovered the vast arc of emission near the Andromeda Galaxy (M31). The region in this image taken with luminance and OIII filters includes the dark nebula LDN 1400 and the blue OIII arc of the supernova remnant G150.3+4.5, also known as Thor’s Lightning. But the new find here is the small oval shell around the star, at lower left, known as CI Camelopardalis, an X-ray binary system. The shell is the debris of a nova that occurred in the system between 1,500 and 2,200 years ago.