This enormous mosaic of Stephan’s Quintet, a visual grouping of galaxies in the constellation of Pegasus, is the largest image captured by the NASA/ESA/CSA James Webb Space Telescope to date. It is constructed from almost 1,000 separate image files and provides new insights into how galactic interactions may have driven galaxy evolution in the early Universe.
Discovered by the French astronomer Édouard Stephan in 1877, the Stephan’s Quintet is a visual grouping of five galaxies in the constellation of Pegasus.
Four of the five galaxies — NGC 7317, NGC 7318A, NGC 7318B, and NGC 7319 — form a physical association: the Hickson Compact Group 92 (HCG 92).
The fifth and leftmost galaxy, NGC 7320, is well in the foreground compared with the other four.
NGC 7320 resides 40 million light-years from Earth, while the other four galaxies are about 290 million light-years away.
“This proximity provides us a ringside seat for witnessing the merging and interactions between galaxies that are so crucial to all of galaxy evolution,” Webb astronomers said.
“Rarely do scientists see in so much detail how interacting galaxies trigger star formation in each other, and how the gas in these galaxies is being disturbed.”
“Stephan’s Quintet is a fantastic laboratory for studying these processes fundamental to all galaxies.”
Tight groups like HCG 92 may have been more common in the early Universe when their superheated, infalling material 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 24 million times the mass of the Sun. It is actively pulling in material and puts out light energy equivalent to 40 billion Suns.
Webb studied NGC 7319’s active galactic nucleus in great 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 Webb team with a ‘data cube,’ or collection of images of the galactic core’s spectral features.
Much like medical magnetic resonance imaging (MRI), the IFUs allow scientists to ‘slice and dice’ the information into many images for detailed study.
Webb pierced through the shroud 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.
“In NGC 7320, the leftmost and closest galaxy in the visual grouping, Webb was able to resolve individual stars and even the galaxy’s bright core,” the researchers said.
“As a bonus, Webb revealed a vast 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 a bounty of valuable, new information.”
“For example, it will help scientists understand the rate at which supermassive black holes feed and grow.”
“Webb also sees star-forming regions much more directly, and it is able to examine emission from the dust — a level of detail impossible to obtain until now.”
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