Shining like a bright beacon amid a sea of galaxies, Arp 220 lights up the night sky in this view from NASA’s James Webb Space Telescope. Actually two spiral galaxies in the process of merging, Arp 220 shines most brightly in infrared light, making it an ideal target for Webb. It is an ultraluminous infrared galaxy (ULIRG) with a luminosity of more than a trillion suns. By comparison, our galaxy, the Milky Way, has a much more modest luminosity of about ten billion suns.
Located 250 million light-years away in the constellation of Serpens, the Serpent, Arp 220 is the 220th object in Halton Arp. Atlas of peculiar galaxies. It is the closest ULIRG and the brightest of the three closest galactic mergers to Earth.
The collision of the two spiral galaxies began about 700 million years ago. It caused a huge burst of star formation. About 200 huge star clusters reside in a dusty, compact region about 5,000 light-years across (about 5 percent the diameter of the Milky Way). The amount of gas in this tiny region is equal to all the gas in the entire Milky Way.
Previous radio telescope observations revealed about 100 supernova remnants in an area less than 500 light-years. NASA’s Hubble Space Telescope discovered the nuclei of parent galaxies separated by 1,200 light-years. Each of the cores has a rotating ring of star formation that emits the dazzling infrared light so evident in this view of Webb. This dazzling light creates diffraction spikes, the starburst feature that dominates this image.
On the outskirts of this merger, Webb reveals faint tidal tails, or material pulled from galaxies by gravity, depicted in blue, evidence of the galactic dance taking place. Organic material represented in reddish orange appears in streams and filaments along Arp 220.
Webb saw the Arp 220 with its Near Infrared Camera (NIRCam) and Mid Infrared Instrument (MIRI).