When galaxies merge, the gravitational fields can stir gases, dramatically accelerating star formation. The end result is known as a starburst galaxy, and the JWST has turned its powerful eye to one of the most impressive examples, IC 1623, also known as VV 114.
Lying 270 million light-years from Earth in the constellation Cetus the Whale, IC 1623 has been a favorite of powerful telescopes for a while. Hubble has taken famous images of the galactic pair, but JWST has once again revealed its capacity to take things to another level.
The JWST’s image outshines Hubble’s not only because of its larger mirror, but because it sees so much further into the infrared. The lower galaxy in the above image, known as IC 1623B, is largely hidden at optical wavelengths by clouds of dust. Infrared radiation is less likely than optical light to be blocked by dust, which is one of the reasons the JWST was chosen to operate at those wavelengths. As can be seen in the Hubble image, IC 1623A is bright at optical and ultraviolet wavelengths, a product of many bright star clusters
Hubble’s version of IC 1623 also shows one bright galaxy, but the other is shrouded by dust. Image credit: NASA, ESA. The Hubble Heritage (STScl/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
The two component galaxies’ cores are currently separated by about 25,000 light years. The contrast between the colors at which they are bright is considered the most extreme of merging galaxies in the local universe.
IC 1623B is known to be rich in warm and dense gas, which is also abundant in the overlapping area between the merging galaxies, creating plenty of raw material for star formation.
Comparison of IC1623 as seen by the Hubble and two instruments on the JWST. Left: Optical Hubble/WFC3 & ACS. Middle: Near-infrared Webb/NIRCam. Right: Mid-infrared Webb/MIRI. In the MIRI image, only the bright core, heated gas and bubbles of star formation are visible. Image credit: ESA/Webb, NASA & CSA, L. Armus & A. Evans