by Quentin Parker (University of Hong Kong)

Parker et al. (2015) report the discovery of the closest collisional ring galaxy to the Milky Way. Such rare systems occur due to “bulls-eye” encounters between two reasonably matched galaxies. The recessional velocity of about 840 km/s is low enough that it was detected in the AAO/UKST Survey for Galactic Halpha emission (shown in red colors above). The distance is only 10.0 Mpc and the main galaxy shows a full ring of star forming knots, 6.1 kpc in diameter surrounding a quiescent disk. The smaller assumed “bullet” galaxy also shows vigorous star formation. The spectacular nature of the object had been overlooked because of its location in the Galactic Plane (b = -7.9 degr) and proximity to a bright star and even though it is the 60th brightest galaxy in the HI Parkes All Sky Survey (HIPASS) . – The galaxy is known as ESO179-IG013 and HIPASS J1647-57 (Koribalski et al. 2004).

Reference: Parker, Zijlstra, Stupar, Cluver, Frew, Bendo, Bojicic 2015, MNRAS, in press