Arp 220: Arp 220 appears to be a single, odd-looking galaxy, but is in fact a nearby example of the aftermath of a collision between two spiral galaxies. It is the brightest of the three galactic mergers closest to Earth, about 250 million light-years away in the constellation of Serpens, the Serpent. The collision, which began about 700 million years ago, has sparked a cracking burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5,000 light-years across (about 5 percent of the Milky Way's diameter). The amount of gas in this tiny region equals the amount of gas in the entire Milky Way Galaxy. The star clusters are the bluish-white bright knots visible in the Hubble image. Arp 220 glows brightest in infrared light and is an ultraluminous infrared galaxy. Previous Hubble observations, taken in the infrared at a wavelength that looks through the dust, have uncovered the cores of the parent galaxies 1,200 light-years apart. Observations with NASA's Chandra X-ray Observatory have also revealed X-rays coming from both cores, indicating the presence of two supermassive black holes. Arp 220 is the 220th galaxy in Arp's Atlas of Peculiar Galaxies. 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 24th April 2008.

Name: Arp 220, IC 1127
Type: Local Universe : Galaxy : Type : Interacting
Category: AnniversaryGalaxies
Constellation: Serpens Caput
Distance: 250 million light years
Release date: 24 April 2008, 15:00
Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

CGCG436-030: CGCG436-030, the eye-catching spiral galaxy in the image, shows a very pronounced curling tail. The companion galaxy, located to the bottom-right of the image, displays an intricate structure, including a number of trails that extend quite far out from its core. The bright star that appears between the two galaxies does not belong to the interacting system and is located within the Milky Way. IRAS 01173+1405 is located in the constellation of Pisces, the Fish, about 400 million light-years away. 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 24th April 2008.

Name: CGCG436-030, IRAS 01173+1405, LEDA 4798
Type: Local Universe : Galaxy : Type : Interacting
Category: AnniversaryGalaxies
Constellation: Pisces
Distance: 400 million light years
Release date: 24 April 2008, 15:00
Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

ESO 148-2: ESO 148-2 is a beautiful object that resembles an owl in flight. It consists of a pair of former disc galaxies undergoing a collision. The cores of the two individual galaxies - seen at the centre of the image - are embedded in hot dust and contain a large number of stars. Two huge "wings" sweep out from the centre and curve in opposite directions. These are tidal tails of stars and gas that have been pulled from the easily distorted discs of the galaxies. This "cosmic owl" is one of the most luminous infrared galaxies known and is located some 600 million light-years away from Earth. 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 24th April 2008.

Name: ESO 148-2
Type: Local Universe : Galaxy : Type : Interacting
Category: AnniversaryGalaxies
Constellation: Tucana
Distance: 550 million light years
Release date: 24 April 2008, 15:00
Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)