When gravity—an invisible yet ubiquitous force—bends and distorts light from distant galaxies, Earthbound observers get a rare glimpse of elusive cosmic phenomena. And the weirder the glitch, the more insightful the finding, as a team of astronomers recently discovered.
These glitches are formally referred to as Einstein Crosses. As light from a distant galaxy travels toward our observatories, the gravitational force of galaxies closer to us bends that light, creating an image of four bright dots arranged like a cross. But astronomers spotted an Einstein Cross with an additional fifth image they couldn’t explain.
Further analysis revealed that a “massive dark matter halo” likely caused this unusual cosmic pattern, the researchers report. Their findings were published on September 16 in The Astrophysical Journal.
Not a glitch in the data
As with many great discoveries in astronomy, the team was initially studying something else. In this case, the researchers had the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile trained on HerS-3, a dusty galaxy located 11.6 billion light-years from Earth.
Everything looked normal until a pesky fifth object kept appearing in their data. At first, they suspected a technical issue on their end. But no matter how hard they tried, the fifth image wouldn’t go away.
“We were like, ‘What the heck?’” Pierre Cox, study lead author and research director at the French National Centre for Scientific Research, recalled in a release. “It looked like a cross, and there was this image in the center. “I knew I had never seen that before.”
“I said, ‘Well, that’s not supposed to happen,’” added Charles Keeton, study co-author and an astrophysicist at Rutgers University, in the same release. “You can’t get a fifth image in the center unless something unusual is going on with the mass that’s bending the light.”
Science takes a dark turn
Later, Keeton and his colleagues ran computer simulations of the gravitational lensing used to capture this five-pronged Einstein Cross. They were baffled to find that no “reasonable configuration using just the [four] visible galaxies” fit the data.
... continue reading