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25th of August 2015
Kathryns Wheel: A spectacular galaxy collision discovered in the Galactic neighbourhood
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

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