A sonic boom many times larger than our Milky Way has been spotted by NASA’s James Webb Space Telescope (JWST) – and it was formed during a galactic invasion.
JWST, along with the Atacama Large Millimeter/submillimeter Array (ALMA), observed that galaxy NGC 7318b entered the five within Stephan’s quintet at 1.8 million miles per hour – a speed that would take you from Earth to the Moon, would only last eight minutes
The event created a shock wave that propagated through the interstellar plasma and started a “recycling plant” for warm and cold molecular hydrogen gas between the five galaxies.
The discovery allowed scientists to zoom in on three key regions of Stephen’s quintet in extreme detail and, for the first time, get a clear picture of how the hydrogen gas is moving and continuously being formed.
An invasion took place 270 million light-years from Earth as a galaxy sped through Stephan’s quintet at 1.8 million miles per hour
Philip Appleton, an astronomer and principal scientist at Caltech’s Infrared Processing and Analysis Center (IPAC), said in a statement, “As this intruder plunges into the group, it collides with an old gas streamer, likely caused by a previous interaction between them became two of the other galaxies and caused the formation of a huge shock wave.
“As the shock wave passes through this clumpy streamer, it creates a highly turbulent or unstable cooling layer, and in the regions affected by this violent activity, we see unexpected structures and recycling of molecular hydrogen gas.
“This is important because molecular hydrogen is the raw material from which stars can ultimately form. So understanding its fate will tell us more about the evolution of Stephan’s quintet and galaxies in general.”
Stephan’s quintet is a group of five galaxies – NGC 7317, NGC 7318a, NGC 7318b, NGC 7319 and NGC 7320 – generally located about 270 million light-years from Earth in the constellation Pegasus.
The cosmic formation is notable for being the first compact galaxy group ever discovered, in 1877.
What makes Stephen’s quintet unique is that a galaxy collision usually triggers a burst of star formation, but where this vigorous activity occurs there is little to no star formation — and scientists are still baffled as to why.
The region at the center of the shock wave, dubbed Field 6, showed a huge cloud of cold molecules being broken apart and stretched into a long tail of warm molecular hydrogen and recycled repeatedly through the same phases.
“What we’re seeing is a huge cloud of cold molecules breaking up in super-hot gas, and interestingly the gas doesn’t survive the shock, it just goes through warm and cold phases,” Appleton said.
“We don’t fully understand these cycles yet, but we do know that the gas is recycled because the length of the tail is longer than the time it takes for the clouds that make it up to be destroyed.”
In the center, Field 5, astronomers identified two cold gas clouds linked by a stream of warm molecular hydrogen gas, marked by a high-speed collision, feeding the warm gas envelope around the region.
The third region, Field 4, showed a more stable, less turbulent environment where hydrogen gas collapsed and formed what scientists believe to be a small dwarf galaxy in formation.
The invasion created a shock wave that propagated through the interstellar plasma, starting a “recycling plant” for warm and cold molecular hydrogen gas between the five galaxies. It allowed scientists to zoom in on three key regions of Stephen’s quintet in extreme detail
Pierre Guillard, researcher at the Institut d’Astrophysique and co-researcher on the project, said: “In field 4, pre-existing large clouds of dense gas are likely to have become unstable due to the shock and collapsed to form new stars, as we expect.
“The shock wave in the intergalactic medium from Stephan’s quintet has formed as much cold molecular gas as we have in our own Milky Way, and yet it is forming stars much more slowly than expected.
“Understanding why this material is sterile is a real challenge for theoreticians. Additional work is needed to understand the role of high turbulence and efficient mixing between cold and hot gas.’
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