The galactic collision that created Arp 148 produced a shock wave that gave this odd galaxy its jellyfish-like shape.
Astronomers think the shock wave first drew matter into the central region, then caused dust and gases to spread outward in a ring. The elongated section perpendicular to the ring suggests the merger is still ongoing.
Arp 148 lies about 500 million light-years away in the constellation Ursa Major, also known as the Big Dipper.
Image by NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech)