Plethora of interacting galaxies on Hubble’s birthday   Arp 148 shows the aftermath of an encounter between two galaxies, resulting in a ring-shaped galaxy and a long-tailed companion. The collision between the two parent galaxies produced a shockwave effect that first drew matter into the centre and then caused it to propagate outwards in a ring. The elongated galaxy perpendicular to the ring suggests that Arp 148 is a unique snapshot of an ongoing collision. Infrared observations reveal an obscured region that appears as a dark dust lane across the nucleus in optical light. Arp 148 is nicknamed 'Mayall’s object' and is located in the constellation of Ursa Major, the Great Bear, approximately 500 million light-years away. This interacting pair of galaxies is included in Arp’s catalogue of peculiar galaxies as number 148. This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24 April 2008.   This Hubble image of ESO 77-14 is a stunning snapshot of a celestial dance performed by a pair of similar sized galaxies. Two clear signatures of the gravitational tug of war between the galaxies are the bridge of material that connects them and the disruption of their main bodies. The galaxy on the right has a long, bluish arm while its companion has a shorter, redder arm. This interacting pair is in the constellation of Indus, the Indian, some 550 million light-years away from Earth. The dust lanes between the two galaxy centres show the extent of the distortion to the originally flat discs that have been pulled into three-dimensional shapes. This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24 April 2008.   Interacting galaxies are found throughout the Universe, sometimes dramatic collisions that trigger bursts of star formation, on other occasions as stealthy mergers that form new galaxies. A series of 59 new images of colliding galaxies, largest collection ever published simultaneously, has been released from archived raw Hubble images to mark the 18th anniversary of the telescope’s launch. Release date: 6 May 2008