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Euclid Space Telescope Uncovers Stunning Einstein Ring in NGC 6505

On July 1, 2023, the Euclid space telescope was launched, embarking on a mission to delve into the mysteries of the dark universe. Following its launch, scientists and engineers meticulously performed checks to ensure the spacecraft’s systems were functioning correctly before commencing its observational survey.

In September 2023, during the initial testing phase, Euclid began transmitting images back to Earth. While some of these images were intentionally out of focus, Bruno Altieri, an archive scientist for Euclid, noticed an intriguing detail in one particularly blurry image and decided to investigate further. “I look at the data from Euclid as it comes in,” Altieri noted. “Even from that first observation, I could see it, but after Euclid made more observations of the area, we could see a perfect Einstein ring. For me, with a lifelong interest in gravitational lensing, that was amazing.”

This Einstein ring, a rare cosmic phenomenon, was found within the galaxy NGC 6505, located approximately 590 million light-years from Earth. Remarkably, this is the first detection of the accompanying ring of light surrounding its nucleus, made possible by Euclid’s advanced instrumentation.

The ring observed around NGC 6505 consists of light distorted by gravitational lensing from a more distant galaxy, which is situated about 4.42 billion light-years away. The light from this background galaxy has been warped as it traveled through the gravitational field of NGC 6505. Interestingly, this distant galaxy has not been previously recorded and remains unnamed.

An Intriguing Discovery

Conor O’Riordan, a lead author from the Max Planck Institute for Astrophysics who analyzed the ring, explained, “An Einstein ring is an example of strong gravitational lensing. All strong lenses are special, because they’re so rare, and they’re incredibly useful scientifically. This one is particularly special, because it’s so close to Earth and the alignment makes it very beautiful.”

According to Albert Einstein’s general theory of relativity, light is bent in the vicinity of massive astronomical objects, allowing these bodies to act like vast lenses. The extent of this bending increases with the mass of the object, such as galaxies or clusters of galaxies, enabling the visibility of light from galaxies that would otherwise be obscured. In optimal alignment, the light from a distant galaxy bends around the foreground object, creating a stunning ring—the Einstein ring. These formations provide invaluable insights into cosmic phenomena, including the expansion of the universe, the characteristics of dark matter and dark energy, and the gravitational effects experienced by the light from background sources.

Valeria Pettorino, ESA Euclid Project Scientist, remarked, “It is intriguing that this ring was observed within a well-known galaxy, which was first discovered in 1884. The galaxy has been known to astronomers for a very long time. Yet this ring was never observed before. This demonstrates how powerful Euclid is, finding new things even in places we thought we knew well.”

Broader Implications for Astronomy

As Euclid continues its exploration of the universe, it aims to provide a deeper understanding of galactic formation and expansion over cosmic history, shedding light on the roles of gravity, dark energy, and dark matter. The telescope is set to map over one-third of the sky, investigating billions of galaxies up to 10 billion light-years away.

The discovery of approximately 100,000 strong lenses is anticipated, yet to identify one this remarkable and this close to Earth is extraordinary. Previously, fewer than 1,000 strong lenses had been documented, and even fewer imaged with high resolution. O’Riordan added, “Euclid is going to revolutionize the field, with all this data we’ve never had before.” While this Einstein ring is a fascinating find, the primary mission of Euclid is to detect the subtler effects of weak gravitational lensing, where background galaxies appear slightly stretched or displaced. Analyzing these phenomena will require examining billions of galaxies as Euclid begins its extensive sky survey on February 14, 2024, creating an unprecedented 3D map of the universe.

More information:
Euclid: A complete Einstein ring in NGC 6505, Astronomy and Astrophysics (2025). DOI: 10.1051/0004-6361/202453014

Source
phys.org