An international space telescope mission that is currently mapping the dark Universe has discovered a rare ‘Einstein Ring’ in a galaxy not far away.
Scientists from Durham University’s Department of Physics are among the founders of the European Space Agency’s (ESA) Euclid telescope project, which is mapping out the structure of the Universe across more than a third of the sky.
The telescope is currently in space, capturing incredibly detailed images of the Universe to further our understanding of how it has expanded and formed over its cosmic history.
And scientists analysing some of the first Euclid images have made a fascinating discovery – an Einstein Ring in a galaxy called NGC 6505.
An Einstein Ring is a rare phenomenon that occurs when a ring of light that forms when a massive object, like a galaxy cluster, bends light from a distant galaxy.
The phenomenon is caused by gravitational lensing; a result of Albert Einstein's theory of General Relativity which predicts that light will bend around objects in space, so that they focus the light like a giant lens.
This newly discovered Einstein Ring turned out to be hiding in plain sight in the galaxy named NGC 6505.
This is around 590 million light-years from Earth, a stone’s throw away in cosmic terms.
However, this is the first time that the ring of light surrounding NGC 6505’s centre has been detected, thanks to Euclid’s high-resolution instruments.
The ring around this foreground galaxy comes from a bright galaxy more than four times farther away.
Light from the background galaxy has been distorted by NGC 6505’s gravity on its way to us.
The far-away galaxy hasn’t been observed before and doesn’t yet have a name.
The research has been published in the journal Astronomy & Astrophysics, and is led by the Max Planck Institute for Astrophysics in Germany and the Institute of Cosmology and Gravitation at the University of Portsmouth, UK.
Professor Richard Massey of the Institute for Computational Cosmology at Durham University, UK, is among the scientists who created the Euclid telescope.
He has been developing its design and science goals for 20 years and is a co-author of the latest study.
Prof Massey said: “The amazing thing about the discovery of this Einstein Ring is that this is a nearby galaxy that has been imaged with telescopes for more than a century.
“But nobody was able to see this ring until now.
“It shows us how powerful the Euclid telescope is, that you can see these fascinating additional details in very familiar surroundings.”
The centre of any galaxy is packed full of stars. The discovery means that the research team can investigate NGC 6505’s stars potentially more accurately than those at the centre of our own Galaxy.
Study co-author, Professor Mathilde Jauzac of Durham University’s Institute for Computational Cosmology, said: “It’s very rare to find one of these rings around a nearby galaxy and we will now be able to weigh its stars – to work out their mass.
“We can combine that with the stars’ motion to establish whether the galaxy is made of a few heavy stars or lots of lightweight ones.
“This is an exciting discovery so early on in Euclid’s mission, which over the next five years will provide us with an astonishing view of the entire night sky in super high-resolution imaging.”
Although this Einstein Ring is stunning, Euclid’s main job is to understand the dark matter that surrounds the outskirts of galaxies, and reaches in vast tracts across intergalactic space.
To map dark matter, scientists will need to analyse billions of galaxies.
Euclid began its detailed survey of the sky on 14 February 2024 and is gradually creating the most extensive 3D map of the Universe yet.
Such an amazing find, so early in its mission, means Euclid is on course to uncover many more hidden secrets.