Euclid Telescope Captures new Einstein Ring around a Galaxy

On February 10th, 2025, ESA unveiled an important discovery made by Euclid. The mission’s telescope captured an Einstein ring, a rare and fascinating phenomenon, in the galaxy NGC 6505.

The ring of light surrounding the centre of the galaxy NGC 6505. Credits: ESA/Euclid/Euclid Consortium/NASA — *The ring of light surrounding the center of the galaxy NGC 6505. Credits: ESA/Euclid/Euclid Consortium/NASA*

NGC 6505 is an Elliptical Galaxy located in the Draco constellation, close to the northern celestial pole. While it is well known and investigated, an Einstein ring had never been identified there before.

A major discovery

This phenomenon is a unique example of strong gravitational lensing. When gravity bends light, images of distant objects appear larger and distorted. Telescopes such as Hubble and James Webb use gravitational lensing to observe much more details and objects than would otherwise be possible.

How the shape of a gravitational lens effects the lensed images. Credits: ESA 2001 — *How the shape of a gravitational lens affects the lensed images. Credits: ESA*

“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.”

— Conor O’Riordan, Max Planck Institute for Astrophysics

If the alignment is just right, the light from the distant galaxy bends to form a spectacular ring around the foreground object. By studying their gravitational effects, we can learn about the expansion of the Universe, detect the influence of dark matter and dark energy, and investigate the background source through its light bent by dark matter.

Einstein ring gravitational lenses, from Hubble Space Telescope. Credits: NASA, ESA, A. Bolton, and the SLACS Team — *Einstein rings gravitational lenses, from Hubble Space Telescope. Credits: NASA/ESA/A. Bolton/SLACS Team*

The ring around NG6505 is composed of light from a more distant, bright galaxy. This background galaxy, located 4.42 billion light-years away, has had its light distorted by gravity on its journey to us. The far-off object has never been observed before and currently does not have a name.

Euclid’s mission and its technologies

Euclid originated from two earlier ESA cosmology mission concepts, DUNE and SPACE. During ESA’s selection process for new science missions under the ‘Cosmic Visions’ program, the two programs were merged into Euclid.

The spacecraft underwent thermal qualification tests at Thales Alenia Space in Cannes (southeastern France). Credits: ESA / S. Corvaja — *The spacecraft underwent thermal qualification tests at Thales Alenia Space in Cannes (southeastern France). Credits: ESA/S. Corvaja*

The telescope was launched aboard a SpaceX Falcon 9 rocket on July 1st, 2023. During the early testing phase, Euclid sent some images back to Earth, deliberately out of focus. In one of those photos, Bruno Altieri saw a hint of a very special phenomenon and investigated it further with subsequent observations.

Euclid’s mission was created to focus on specific techniques: high-resolution visible imaging for weak lensing; near-infrared photometry for distance measurements of galaxies; and determining the exact location of a subset of galaxies using spectroscopy.

The capabilities needed for Euclid result in two separate instruments using different technology. One is the Visible Imager (VIS), an imaging camera in the visible wavelength range, and the other is the Near-Infrared Spectrometer and Photometer (NISP).

Rendering of Euclid’s payload module baseplate, with the two science instruments VIS and NISP mounted. Credits: Airbus and ESA — *Rendering of Euclid’s payload module baseplate, with the two science instruments VIS and NISP mounted. Credits: Airbus/ESA*

The VISible instrument is composed of 36 charged-coupled devices (CCDs), each one having 4000 x 4000 pixels, where each pixel is 12 millionths of a meter square. The NISP instrument is a multi-bandpass, near-infrared camera. It enables the telescope to split up the light of every celestial source along its wavelength, or energy, and produce an intensity spectrum.

A promising start

This important discovery bodes well for the mission’s research objectives. By exploring how the Universe has expanded and formed over its cosmic history, Euclid will reveal more about the role of gravity and the nature of dark energy and dark matter. The mission is producing an extensive 3D map of the Universe, analyzing billions of galaxies.

*Euclid overview of looking at weak lensing of galaxies. Credits: ESA*

“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”, pointed out Valeria Pettorino, ESA Euclid Project Scientist.