Astronomers Spot a Galaxy Smashing Into Its Neighbors at 800 Times the Speed of a Fighter Jet

The first observations from a new instrument on one of the world’s most powerful telescopes have captured an enormous galactic collision in astounding detail, even though it’s 290 million light-years away. Published Friday in the journal Monthly Notices of the Royal Astronomical Society, the findings reveal a powerful shock wave produced by the impact and could shed light on how similar events might have formed the Milky Way and other galaxies.

The astronomical crash took place within a group of five galaxies called Stephan’s Quintet, which gained notoriety as one of the first images released from the James Webb Space Telescope in 2022. Now, it’s been studied with the first observations from a new instrument called the William Herschel Telescope Enhanced Area Velocity Explorer (WEAVE), located on the William Herschel Telescope in La Palma, Spain.

“It’s fantastic to see the level of detail uncovered here by WEAVE,” study co-author Gavin Dalton, an astrophysicist at Oxford University in England, says in a statement. “As well as the details of the shock and the unfolding collision that we see in Stephan’s Quintet, these observations provide a remarkable perspective on what may be happening in the formation and evolution of the barely resolved faint galaxies that we see at the limits of our current capabilities.”

Astronomers found that a galaxy within Stephan’s Quintet called NGC 7318b is smashing through its neighbors at a speed of more than two million miles per hour. It caused a powerful shock similar to the sonic boom of fighter jets—except the top speed of an SR-71 Blackbird jet fighter is around 2,500 miles per hour, so NGC 7318b is moving about 800 times faster, Robert Lea writes for Space.com.

Scientists have been interested in Stephan’s Quintet since its discovery in 1877, because, among other reasons, many of its galaxies repeatedly come close to knocking into each other, and it’s composed of the wreckage left behind from past astronomical collisions. In the words of New Atlas’ Michael Irving, Stephan’s Quintet is “the cosmic equivalent of glass and metal scattered across a road after a car crash.”

“It’s basically a huge, intergalactic field of debris,” lead author Marina Arnaudova, an astrophysicist at the University of Hertfordshire in England, tells Live Science’s Ben Turner.

Now, “the new intruder NGC7318b has smashed into the debris field and compressed the plasma and gas in it,” she adds. “In doing so, it has re-energized the plasma, causing it to glow brightly at radio frequencies, and likely triggered star formation in the process.”

In other words, the impact has released a shock wave traveling several times faster than the speed of sound. As it moves through pockets of cold gas in that galactic region, it rips electrons from atoms, leaving the gas with an electrical charge. However, when the shock wave passes through hot gas, it grows weaker and compresses the gas, generating radio waves. In the statement, researchers say the motion has “reawakened” the system of galaxies.

“This type of galaxy collision in Stephan’s Quintet is a rare chance to see a complex set of galaxies caught in the act of colliding,” Arnaudova explains to Live Science. “As to how it will end up, well it’s likely that it will eventually merge with one of the group members, but not for millions or billions of years, because the sizes and speeds of these things are so vast.”

Researchers say the findings are a testament to what WEAVE might be capable of as its operations continue. The new instrument is a wide-field spectrograph—more plainly, it’s a super-fast mapping device connected to the William Herschel Telescope that can analyze the chemical makeup of stars and gas, per the statement. It does so with a spectroscope, which reveals the elements in stars by producing a barcode-like pattern.

WEAVE’s main goal is to uncover clues about how the Milky Way and other galaxies formed—and how the universe evolved as a whole. For the new study, astronomers combined WEAVE’s data with observations from other instruments, including the Low Frequency Array, the Very Large Array and the James Webb Space Telescope.

While this galactic crash is WEAVE’s first major scientific finding, scientists are excited at the prospect of future revelations.

“I’m sure this is just an early example of the types of discoveries that will be made possible with WEAVE on the William Herschel Telescope in the coming years,” study co-author Marc Balcells, an astrophysicist at the Open University of Catalonia, says in the statement. But so far, he adds, the data from the new telescope “already provide a high-impact result.” (Hopefully, the pun was intended).

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.