The European Space Agency's (ESA) Euclid telescope captured an Einstein ring—a luminous circle formed by the gravitational bending of light around the galaxy NGC 6505.
Researcher Bruno Altieri observed indications of this phenomenon in early test images from the Euclid telescope. "I observe the Euclid data as they arrive," Altieri said, according to Science Alert. "For me, with a lifelong interest in gravitational lensing, that was amazing."
The image reveals NGC 6505 encircled by a near-perfect ring of light originating from a background galaxy positioned 4.42 billion light-years away. The distant galaxy, which has not been observed before and does not yet have a name, has its light bent around NGC 6505 due to gravitational lensing, creating the ring.
Gravitational lensing occurs when the gravity of a massive object, like a galaxy, warps the fabric of spacetime, bending the light from a more distant background object. In rare cases, when there is an ideal alignment between the observer, the foreground galaxy, and the background galaxy, the phenomenon results in a geometrically perfect distortion of light known as an Einstein ring. These rings are powerful tools for astronomers because they reveal hidden objects that would otherwise be unseen and indicate the mass of the intervening galaxy, including any hidden mass in the form of dark matter.
"An Einstein ring as perfect as this is extremely rare," said Professor Stephen Serjeant from the Open University, according to the Manchester Evening News. "This is a beautiful, extraordinary, exciting, and lucky discovery in our first data."
"I find it very intriguing that this ring was observed within a well-known galaxy, which was first discovered in 1884," said Dr. Valeria Pettorino, ESA Euclid Project Scientist. “This proves how powerful Euclid is, finding new things even in places we thought we knew everything," she added.
The Euclid telescope aims to map more than a third of the sky and observe billions of galaxies out to 10 billion light-years.
Conor O'Riordan, an astrophysicist at the Max Planck Institute for Astrophysics, led the research on the discovery. "All strong lenses are special because they're so rare, and they're incredibly useful scientifically," O'Riordan said, according to Science Alert. "Euclid is going to revolutionise the field, with all this data we've never had before," he added.
In the image captured by Euclid, the nearby galaxy NGC 6505—located approximately 590 million light-years from Earth—is surrounded by a ring of light, resembling a halo. The light forming the ring around NGC 6505 comes from another galaxy located directly behind it, 4.42 billion light-years away. This alignment causes the light from the distant galaxy to be warped by the gravitational field of NGC 6505, creating the Einstein ring and revealing the curvature of spacetime due to gravity.
"Finding a strong lens that is so spectacular and so close to Earth is astonishing," said Professor Thomas Collett, according to New Scientist. "To find it in essentially the first, earliest data is spectacularly lucky."
By analyzing the distortion of light from distant galaxies, astronomers can measure the mass of the lensing galaxy in terms of stars and dark matter, inferring the gravitational influence of unseen mass. This provides insights into the nature of the universe and its hidden structures.
In the case of NGC 6505, scientists estimate that it is composed of about 11% dark matter—a relatively small fraction considering that dark matter is believed to dominate the total mass content of the universe.
This article was written in collaboration with generative AI company Alchemiq