NASA's James Webb Space Telescope has captured a stunning image of a pair of galaxies known collectively as Arp 220, which are in the process of merging 250 million light-years away from Earth in the constellation Serpens.
The galaxies, which are spirals like the Milky Way, started blending together 700 million years ago, resulting in the triggering of intense star formation. Over 200 star clusters are packed into an area just 5,000 light-years across in Arp 220's central star-forming ring, and most of the gas in this region is equal to all of the gas in the entire Milky Way galaxy, reports Space.com.
Using two of its high-tech instruments, the Near Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI), James Webb Space Telescope was able to capture the image of Arp 220. The telescope's primary camera, NIRCam, and MIRI, which can snap images as well as capture the light spectra of its targets, were both useful as Arp 220 shines its brightest in infrared wavelengths. The object's light is equivalent to "more than a trillion suns," according to the image description, while the Milky Way's luminosity is about 10 billion suns.
Arp 220 is not the first galactic merger to be observed, and the process unfolds over a long time, even on cosmic timescales. Astronomers believe that Arp 220's galaxies began merging 700 million years ago and are similar to the Milky Way, with similar tails swirling in their outskirts. Researchers think the X-rays recorded by NASA's Chandra X-Ray Observatory hint at supermassive black holes residing at the centers of both galaxies.
Astronomers previously believed that much of Arp 220 hosted heaps of star clusters, but recent research analyzing pictures clicked by NASA's Hubble Space Telescope found that star formation "shut off suddenly everywhere" about 100 million years ago, possibly as a consequence of the merger. It appears that Arp 220 is now in a post-starburst stage, which means it does not produce stars at extreme, short-lived rates, but is instead quiescent.
Arp 220 belongs to a subset of a collection of 338 uncommon galaxies whose shapes astronomers did not understand back in 1966 when American astronomer Halton C. Arp published the Atlas of Peculiar Galaxies. Astronomers do not usually tag two merging galaxies with one name, but Arp 220 is the 220th celestial object in the Atlas of Peculiar Galaxies, and its jumbled shape was explained when researchers later found that it is not one but two galaxies coalescing.