An enormous mosaic of Stephan’s Quintet is the largest image to date from NASA’s James Webb Space Telescope, 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 visual grouping of five galaxies was captured by Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). Credit: NASA, ESA, CSA, STScI

NASA’s James Webb Space Telescope reveals never-before-seen details of the galaxy group called “Stephan’s Quintet” in an enormous new image. The close proximity of this group gives scientists a ringside seat to galactic mergers and interactions. Astronomers rarely 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. In a level of detail never seen before, the image also shows outflows driven by a supermassive black hole in one of the group’s galaxies. Tight galaxy groups like this may have been more common in the early universe when superheated, infalling material may have fueled very energetic black holes.

With its powerful, mid-infrared vision, the Mid-Infrared Instrument (MIRI) shows never-before-seen details of Stephan’s Quintet, a visual grouping of five galaxies. MIRI pierced through dust-enshrouded regions to reveal huge shock waves and tidal tails, gas, and stars stripped from the outer regions of the galaxies by interactions. It also unveiled hidden areas of star formation. The new information from MIRI provides invaluable insights into how galactic interactions may have driven galaxy evolution in the early universe. Credit: NASA, ESA, CSA, STScI

NASA’s Webb Sheds Light on Galaxy Evolution, Black Holes

Best known for being prominently featured in the classic Christmas film, “It’s a Wonderful Life,” Stephan’s Quintet is a stunning visual grouping of five galaxies. Now, NASA’s James Webb Space Telescope reveals Stephan’s Quintet in a new light. This gigantic mosaic is Webb’s largest image to date, covering about one-fifth of the Moon’s diameter. Constructed from almost 1,000 separate image files, it contains over 150 million pixels. The information from Webb provides new insights into how galactic interactions may have driven galaxy evolution in the early universe.

Webb shows never-before-seen details in this galaxy group thanks to its powerful, infrared vision and extremely high spatial resolution. Sparkling clusters of millions of young stars and starburst regions of fresh star birth grace the image. Sweeping tails of gas, dust, and stars are being pulled from several of the galaxies due to gravitational interactions. Most dramatically, the Webb Space Telescope captures huge shock waves as one of the galaxies, NGC 7318B, smashes through the cluster.

The top spectrum, from the black hole’s outflow, shows a region filled with hot, ionized gases, including iron, argon, neon, sulfur, and oxygen as denoted by the peaks at given wavelengths. The presence of multiple emission lines from the same element with different degrees of ionization is valuable for understanding the properties and origins of the outflow.The bottom spectrum reveals that the supermassive black hole has a reservoir of colder, denser gas with large quantities of molecular hydrogen and silicate dust that absorb the light from the central regions of the galaxy. Credit: NASA, ESA, CSA, STScI

Together, 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. In fact, NGC 7320 resides just 40 million light-years from Earth, while the other four galaxies (NGC 7317, NGC 7318A, NGC 7318B, and NGC 7319) are around 290 million light-years away. This is still fairly close in cosmic terms, compared with more distant galaxies billions of light-years away. Studying such relatively nearby galaxies like these helps astronomers better understand structures seen in a much more distant universe.

This proximity provides scientists a ringside seat for witnessing the merging and interactions between galaxies that are so crucial to all of galaxy evolution. Rarely do astronomers witness 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 an excellent “laboratory” for studying these processes fundamental to all galaxies.

Some of the key emission lines seen by NIRSpec are shown in this image and represent different phases of gas. Atomic hydrogen, in blue and yellow, allows scientists to discover the structure of the outflow. Iron ions, in teal, trace the places where the hot gas is located. Molecular hydrogen, in red, is very cold and dense, and traces both outflowing gas and the reservoir of fuel for the black hole. The bright, active nucleus itself has been removed from these images to better show the structure of the surrounding gas. By using NIRSpec, scientists have gained unprecedented information about the black hole and its outflow. Studying these relatively nearby galaxies helps scientists better understand galaxy evolution in the much more distant universe. Credit: NASA, ESA, CSA, STScI

Webb studied the 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 captured these outflows driven by the black hole in a level of detail that has never been 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.

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 obtained by Webb will provide a bounty of valuable, new information. For instance, it will help astrophysicists 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 emissions from the dust – a level of detail that was previously impossible to obtain.

Some of these key emission features are shown in this image. In each case, the blue-colored regions indicate movement toward the viewer and orange-colored regions represent movement away from the viewer. The argon and neon lines are from hot spots of super-heated gas that is highly ionized by the powerful radiation and winds from the supermassive black hole. The molecular hydrogen line is from colder dense gas in the central regions of the galaxy and entrained in the outflowing wind. The velocities are measured by shifts in the wavelengths of a given emission line feature. Credit: NASA, ESA, CSA, STScI

Located in the constellation Pegasus, Stephan’s Quintet was discovered by the French astronomer Édouard Stephan in 1877.