Arp 220

Arp 220 (IC 4553, UGC 9913 ) is the Earth's next example of an ultra- luminous infrared galaxy, with more than 1012 solar luminosities. Arp 220 is 23 ° 30'11 " ( equinox 2000) at a distance of about 75 megaparsecs in right ascension 15h34m57, 1s, declination.

Halton Arp had included this galaxy with the number 220 in his Atlas of unusual galaxies. Let the weak loops and arms in deep optical images along with the actual galaxy suggest that it is caused by the merger of two galaxies. As an exceptionally Arp 220 has been detected in the 1980s by measurements of the infrared telescope IRAS. Their luminosity is much larger than in normal galaxies and escapes for the most part in the far infrared - almost a hundred times more at wavelengths around 100 microns than in blue light at 0.5 microns. The core area of Arp 220 is covered by dust, which swallows the luminosity of the actual source of energy and radiates back in the far infrared.

In the visible picture from the Hubble Space Telescope, the core region of Arp 220 is completely hidden behind thick dust lanes. However, many young bright star clusters have also attention to unusual properties. The Hubble Space Telescope near-infrared penetrates better through the dust and shows the not yet completely fused core regions of the two output galaxies. But even here are the most deeply embedded in the dust regions not yet visible. Studies with the Infrared Space Observatory mid-infrared and with VLBI at radio show that they contain a violent starburst, but also a contribution of an active galactic nucleus can not be excluded.

• Individual galaxy
• Atlas of Peculiar Galaxies