A combination of JWST and HST data showing a new view of ultraluminous infrared galaxy Arp 220. Here, I've tried to cut down on the redness because if I were to simply take all the data and throw it together, much of the galaxy would be lost in a red glare. Instead, the central details are actually visible. This is important because the imagery reveals what I presume to be the cores of the two galaxies that merged to create this single disturbed galaxy, not yet fully merged themselves. Prior to JWST observations two cores were already detected, but these new data reveal them in more detail than before.

Surrounding the center are some splotchy red and orange areas representing the MIRI (Mid-Infrared) data. This is essentially glowing dust. That is, the dust emits light in certain mid-infrared wavelengths, revealing it in much greater detail. In visible light, dust requires background illumination to see it or it is otherwise invisible. The eight faint, fuzzy red lines/bars emanating from the center are diffraction spikes caused by support structures of JWST.

Other interesting features include the blue clusters of younger stars resulting from recent star formation brought about when dust and gas collided as the galaxies orbited and merged with one another. Colorful background galaxies were also revealed in JWST data that were previously invisible or below the signal to noise ratio for HST observations. Note that many individual stars and star clusters are visible within the galaxy, thanks to the resolving power of JWST. What may look like noise in this galaxy is actually resolved stars!

Regarding the processing of this image: It took a long time to smooth this out to an aesthetically pleasing image. The shortwave NIRCam imagery is muddled by fine and coarse banding, which makes for a rather unsightly image if not taken care of. I'd like to thank the makers of the open source project G'MIC and specifically Simeon Schmauß for assisting me in greatly reducing and nearly eliminating the banding problems.

Data from the following proposals were used to create this image: Proposal 2739 (no info as of this post) An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

Reddish orange "screen": JWST MIRI F1130W

Red: JWST NIRCam F444W+F356W+F277W Green: JWST NIRCam F200W+F150W+F090W Blue: HST F814W+F435W