In the first-ever-observed game of “cosmic joust,” one galaxy pierced another with a lance-like ray of radiation, astronomers reported in the journal Nature. The resulting puncture impaired the wounded galaxy’s subsequent star-making abilities.
The dueling galaxies dealt more than just a single blow. They repeatedly charged each other at over 500 miles per second, colliding, then retreating, before positioning themselves for another attack.
“We hence call this system the ‘cosmic joust,’” Pasquier Noterdaeme, an astronomer with the Institut d'Astrophysique de Paris and an author of the paper, said in a press release.
A Galactic Battle in Time
The “galactic battle,” as the press release called it, was captured by combining data from two instruments: the European Southern Observatory’s Very Large Telescope (ESO’s VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA).
However, it wasn’t exactly a fair fight. One galaxy wielded a superior weapon: a quasar that emitted a spear of radiation. Quasars are the cores of some distant galaxies powered by supermassive black holes that emit huge amounts of radiation.
Since both quasars and galaxy mergers happened far more often in the Universe’s first few billion years, the astronomers essentially had to look back in time to see them. Since the light from the cosmic joust took over 11 billion years to reach the instruments, the battle took place when the Universe was about 18 percent of its current age.
Interfering with Star Formation
The observations provide a peek into processes that can impact star formation. The aggressor quasar-possessing galaxy’s radiation release interferes with clouds of gas and dust in victim conventional galaxy. That disruption leaves only the smallest, most dense regions behind — essentially reducing the wounded galaxy’s ability to form stars.
“Here we see for the first time the effect of a quasar’s radiation directly on the internal structure of the gas in an otherwise regular galaxy,” Sergei Balashev, a researcher at the Ioffe Institute in St Petersburg, Russia and an author of the paper, said in press release.
Read More: Light Emitted by a Distant Galaxy Pierces Through the Early Universe's Fog
Future Detailed Collisions in Space
The victim isn’t the only one affected by the process. The astronomers suspect that the collisions feed the supermassive black hole at the the aggressor galaxy’s center. That process essentially fuels the the quasar the energy it needs to continue its attack.
Observations from both telescopes were made using specialized instruments located in Chile’s Atacama Desert. The results are a testament to the new generation of telescopes’ power. Previous observations with weaker instruments showed the jousting galaxies as a single object.
The next generation of instruments, such as ESO’s Extremely Large Telescope could reveal even more details about similar collisions. That telescope, which began construction in the Chilean desert, is scheduled for test operations in 2029 and first observations in 2030.
Read More: How Astronomers Define Where a Galaxy Ends and Interstellar Space Begins
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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
