The European Euclid telescope has photographed a unique cosmic mirage that has been hidden from astronomers for more than a century. It managed to capture the Einstein ring encircling the center of a galaxy close to us.
Perfect ring
The Euclid telescope was launched in July 2023 to study dark matter and dark energy. Before embarking on its scientific program, it took a number of test photos. They were deliberately out of focus, but in one fuzzy image, scientist Bruno Altieri saw a hint of a very unusual phenomenon and decided to take a closer look.
He was right. It turned out that Euclid had managed to photograph the Einstein ring. This is a rare phenomenon by itself, but what’s even more amazing is that it’s literally hiding in plain sight. The ring surrounds a galaxy called NGC 6505. It is about 590 million light-years away from Earth, which is quite small by cosmic standards. But although NGC 6505 was discovered back in 1884, only thanks to Euclid, astronomers were able to discover that it was surrounded by the Einstein ring.
What is the Einstein ring
The general theory of relativity predicts that, like a lens, the gravity of massive objects can change direction and amplify light streams from more distant celestial bodies, producing bizarre cosmic mirages. Astronomers actively use gravitational lenses in their work, because it allows them to study distant objects that under normal conditions would not be able to view even the most powerful of existing telescopes.
One of the most spectacular varieties of gravitational lenses is called the Einstein ring. It occurs when the lens object and a more distant background object are in a straight line relative to the Earth. In this case, the light of the latter bends to form a spectacular ring around the foreground object.
The Einstein ring, photographed by Euclid, is made up of light from a more distant galaxy that is 4.42 billion light-years away. Since it has never been observed before, it does not yet have a formal designation.
Astronomers have managed to find about a thousand gravitational lenses so far. But the Euclid finding is a special case. The ring perfectly surrounds a long-known and relatively close galaxy, allowing for high-resolution photography. According to the scientists, the discovery clearly demonstrates the power of Euclid’s tools. It is expected to be able to detect up to 100,000 strong gravitational lenses during its lifetime.
According to ESA
