A rare Einstein ring has been detected by the Euclid space telescope, offering valuable insights into dark matter distribution. The phenomenon, created by the gravitational lensing effect of a galaxy located nearly 600 million light-years away, has provided researchers with a means to analyse the mass and composition of the lensing galaxy. The discovery occurred as Euclid commenced its mission to construct an extensive 3D map of the universe.

Dark Matter Insights from Gravitational Lensing

According to research published in Astronomy & Astrophysics, the gravitational lens responsible for this Einstein ring has been identified as the galaxy NGC 6505. Situated around 590 million light-years from Earth, the galaxy’s mass is significant enough to bend light from a more distant source, forming a nearly perfect circle. This alignment has enabled scientists to examine the lensing galaxy’s central region, where dark matter presence is notably lower than expected.

As reported by space.com, the research team has referred to this structure as “Altieri’s lens,” named after astronomer Bruno Altieri, who played a key role in its identification. The lensing effect allows astronomers to measure the mass distribution of NGC 6505, revealing that dark matter accounts for approximately 11 percent of the central region’s total mass. Giulia Despali, a researcher at the University of Bologna, stated that this percentage contrasts sharply with dark matter’s estimated 85 percent contribution to the universe’s overall mass.

Einstein Rings and Their Significance

The discovery of an Einstein ring aligns with Albert Einstein’s general theory of relativity, which predicts the warping of space-time by massive objects. Strong gravitational lenses, such as the one seen in NGC 6505, provide a method for mapping the otherwise invisible distribution of dark matter. Massimo Meneghetti, a researcher at the National Institute for Astrophysics, explained that while galaxies at this distance are not typically powerful enough to form strong lenses, NGC 6505’s dense central mass has enabled this rare event. The nearly perfect symmetry of the ring suggests a precise alignment between the background light source, the lensing galaxy, and the telescope.

Euclid’s Mission and Future Discoveries

The Euclid telescope, launched in July 2023 by the European Space Agency (ESA), is designed to examine the dark universe by mapping cosmic structures over the past 10 billion years. Strong gravitational lenses such as Altieri’s lens are expected to be rare, with scientists estimating that no more than 20 similar structures will be identified over the mission’s course.

Despite this rarity, Euclid is projected to locate over 100,000 additional gravitational lensing events in its study of 14,000 square degrees of the sky. This extensive mapping will assist researchers in analysing the distribution of dark matter and dark energy across different galaxies and their evolution over time.