Universe records most powerful 'sonic booms' 290M light-years from Earth
A galaxy in Stephan's Quintet, a collection of five galaxies, has been seen hurtling through space at an incredible speed of 3.2 million km/h. The high-speed galaxy, called NGC 7318b, crashed into the other four galaxies in the cluster. The collision produced the most powerful shockwaves ever witnessed in the universe, similar to a "sonic boom from a jet fighter," researchers said.
Discovery made by Spanish telescope
The remarkable phenomenon was witnessed by the William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE) in La Palma, Spain. The results were published in the journal Monthly Notices of the Royal Astronomical Society on November 22. Discovered nearly 150 years ago, Stephan's Quintet is a massive intergalactic field of debris. As NGC 7318b sped through it, debris from past galactic collisions was reignited.
Stephan's Quintet: A galactic crossroad of past collisions
Stephan's Quintet has been decribed as "galactic crossroad where past collisions between galaxies have left behind a complex field of debris," by Marina Arnaudova, an astronomer at the University of Hertfordshire and study's lead author. Arnaudova further explained that the "dynamical activity in this galaxy group has now been reawakened by a galaxy smashing through it at an incredible speed of over two million mph, leading to an immensely powerful shock, much like a sonic boom from a jet fighter."
Shockwave's dual nature and interaction with gases
The shockwave generated by the collision was two-pronged. Arnaudova explained that as the shock travels through pockets of cold gas, it moves at hypersonic speeds — several times the speed of sound in Stephan's Quintet's intergalactic medium. This is strong enough to rip electrons off atoms, creating a glowing trail of charged gas.
Shockwave's interaction with hot gas
Soumyadeep Das, a PhD student at the University of Hertfordshire, clarified that when the shock interacts with surrounding hot gas, it compresses it rather than causing a major disruption. This compression produces radio waves that are detected by radio telescopes such as the Low-Frequency Array (LOFAR). Stephan's Quintet was discovered by French astronomer Édouard Stephan in the 19th century. It is about 290 million light-years from Earth, "locked in a cosmic dance of repeated close encounters," according to NASA.
