Shock waves from the violent collision between the intruder galaxy and Stefan Quintet are helping astronomers understand how turbulence affects gas in the intergalactic medium. New observations by the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST) showed that a sonic boom several times the size of the Milky Way started a facility to process hot and cold molecular hydrogen. Not only that, scientists have discovered that a giant cloud disintegrated into a warm fog of gas, a possible collision of two clouds, spatters of hot gas around them, and a new galaxy formed. The observations were presented at a press conference at the 241st meeting of the American Astronomical Society (AAS) in Seattle, Washington on Monday, January 9, 2023.

The Stefan Quintet is a group of five galaxies – NGC 7317, NGC 7318a, NGC 7318b, NGC 7319 and NGC 7320 – normally located about 270 million light-years from Earth in the constellation Pegasus. The group is a pristine laboratory for the study of galactic collisions and their effects on the environment. provides. As a rule, collisions and mergers of galaxies cause an explosion of star formation; That’s not the case with Stefan’s quintet. Instead, this violent activity takes place in the intergalactic medium, as far away from galaxies as possible, where there is virtually no star formation to obscure vision.

Astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) and the James Webb Space Telescope (JWST) to find out exactly what’s going on in Stefan’s quintet of hot, warm, and cold molecular gas that behaves somewhat strangely. This animated video highlights Observation Zones 4, 5 and 6, the region where the team discovered that the turbulence caused by the giant shock wave created a reprocessing facility for hot and cold molecular gas, causing Quintet’s strange structural behavior. Area 6 showed the first signs of a waste treatment facility where the region is stretching a giant cloud of cold molecules toward a hot molecular hydrogen tail. Area 5 astonishingly revealed a high-speed collision in which a ball of gas passed through a molecular cloud, forming a ring and connecting two clouds of cold gas. The most normal, Area 4, is a relatively stable environment that perhaps allows a small dwarf galaxy to grow.

This open window into the universe allowed astronomers to observe what happens when one of the galaxies, NGC 7318b, crashes into the group at a relative speed of about 800 km/s. At this speed, the journey from Earth to the Moon would take only eight minutes. “When this intruder hits the cluster, it collides with an ancient gas flow, possibly caused by the previous interaction between the two other galaxies, and triggers the generation of a giant shock wave,” said astronomer and senior scientist Philip Appleton. IPAC at Caltech and lead researcher on the project. “When the shock wave travels through this lumpy strip, it creates a very turbulent or unstable cooling layer, and we see unexpected structures and recycling of molecular hydrogen gas in the regions affected by this turbulent activity. This is important because molecular hydrogen forms the raw material that can eventually form stars, so understanding its fate will help us to understand its fate.” It will give more information about the evolution of the Stefan quintet and galaxies in general.”