James Webb Sheds Light on Galaxy Evolution

Stephan’s Quintet, which is a group of five galaxies, is best known for being prominently featured in the holiday classic film, “It’s a Wonderful Life.” It was discovered by the French astronomer Édouard Stephan in 1877 and is located in the constellation Pegasus.  NASA’s James Webb Space Telescope reveals Stephan’s Quintet in a new light. This extensive mosaic is James Webb’s one of the largest images, covering about one-fifth of the Moon’s diameter. It contains over 150 million pixels and is constructed from almost 1,000 separate image files. The information from James Webb provides new insights into how galactic reactions may have driven galaxy evolution in the early universe.

The five galaxies of Stephan’s Quintet
Image credit: NASA, ESA, CSA, and STScI

James Webb's powerful, infrared vision and extremely high spatial resolution, it shows never-before-seen details in this group of galaxies. Million sparkling clusters of young stars and starburst regions of fresh star birth grace the image. Boundless tails of gas, dust, and stars are being pulled from several of the galaxies due to gravitational interactions. Most dramatically, James Webb captures huge shock waves as one of the galaxies, NGC 7318B, smashes through the cluster.

The five galaxies of Stephan’s Quintet are also known as the Hickson Compact Group 92 (HCG 92). Although called a “quintet,” only four of the galaxies are actually close together and caught up in a cosmic dance. The fifth and leftmost galaxy, called NGC 7320, is well in the foreground compared with the other four. NGC 7320 resides 40 million light-years away, while the other four galaxies (NGC 7317, NGC 7318A, NGC 7318B, and NGC 7319) are about 290 million light-years away from Earth. In cosmic terms, this is still fairly close compared with more faraway galaxies billions of light-years away. Studying such relatively nearby galaxies like these helps scientists better understand structures seen in a much more distant universe.

NGC 7317, NGC 7318A and  NGC 7318B, NGC 7319, and NGC 7320(Left to right respectively)

This proximity provides astronomers a ringside seat for witnessing the merging and interactions between galaxies that are so critical to all of galaxy evolution. Infrequently scientists see in so much detail how interacting galaxies trigger star formation in each other, and how the gas in these galaxies is being interrupted. Stephan’s Quintet is a fantastic place for studying these processes fundamental to all galaxies in the universe.

Compressed groups like this group of galaxies may have been more common in the early universe when their superheated, material which is moving under gravity may have fueled very energetic black holes called quasars. Even today, the topmost galaxy in the group – NGC 7319 – harbors an active galactic nucleus, a supermassive black hole that has 24 million times the mass of the Sun. It is actively pulling in material and puts out light energy equivalent to 40 billion Suns. 

NGC 7319
Photo credit: NASA

James Webb studied the active galactic nucleus in detail with the Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI). These instruments’ integral field units (IFUs) – which are a combination of a camera and spectrograph – provided the James Webb team with a “data cube,” or collection of images of the galactic core’s spectral features.

JWST optical devices
Photo Credit: ESA(European Space Agency)

JWST Mid Infrared Instrument (MIRI)

Much like medical magnetic resonance imaging (MRI), the IFUs allow scientists to “slice and dice” the information into many images for detailed study. James Webb pierced through the cover of dust surrounding the nucleus to reveal hot gas near the active black hole and measure the velocity of bright outflows. The telescope saw these outflows driven by the black hole in a level of detail never seen before.

James Webb was able to resolve individual stars and even the galaxy’s bright core in NGC 7320 which is the leftmost and closest galaxy in the visual grouping, 

Webb also revealed a boundless sea of thousands of distant background galaxies reminiscent of Hubble’s Deep Fields.

Combined with the most detailed infrared image ever of Stephan’s Quintet from MIRI and the Near-Infrared Camera (NIRCam), the data from Webb will provide premium valuable, new information. For example, it will help scientists understand the feeding and growth rate of supermassive black holes. Webb also sees star-forming regions much more directly, and it is able to examine emissions from the dust – a level of detail impossible to obtain until now.