The Euclid Space Telescope has captured a remarkable image showing an extremely rare phenomenon: a ring of light around the center of a galaxy, known as an Einstein Ring. These structures appear in telescope images due to the distorting effects of gravity, and they allow researchers to study distant galaxies which might otherwise be insibile.
The ring was spotted around the center of galaxy NGC 6505, located in our cosmic back yard at just 590 million light-years from Earth. The ring itself is created by light from a background galaxy which is a whopping 4.42 billion light-years away, and which has been distorted into the ring shape due to the mass of the foreground galaxy. This effect, called gravitational lensing, is not uncommon — but it is rare for the galaxies to be aligned just so, to create a perfect ring of light.
“An Einstein ring is an example of strong gravitational lensing,” said lead researcher Conor O’Riordan of the Max Planck Institute for Astrophysics, Germany. “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.”
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The object was observed purely by chance, while the Euclid telescope was still in its testing phase in September 2023. Even though these images were fuzzy and out of focus, one of the researchers working on the images spotted clues that there could be something special to see and looked more closely.
“I look at the data from Euclid as it comes in,” explained Euclid Archive Scientist Bruno Altieri. “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.”
The Einstein ring is exciting for researchers not only because it is rare to see one, but also because it can help them study phenomena like dark matter and dark energy, which are invisible but can be studied by looking for their gravitational effects. Euclid will be studying dark matter by looking for these kinds of effects.
“I find it very intriguing that this ring was observed within a well-known galaxy, which was first discovered in 1884,” said Valeria Pettorino, Euclid Project Scientist. “The galaxy has been known to astronomers for a very long time. And yet this ring was never observed before. This demonstrates how powerful Euclid is, finding new things even in places we thought we knew well. This discovery is very encouraging for the future of the Euclid mission and demonstrates its fantastic capabilities.”
“Euclid is going to revolutionize the field, with all this data we’ve never had before,” said O’Riordan.
The research is published in the journal Astronomy & Astrophysics.