Einstein Ring

Spectacular discoveries in physics are currently being made not at particle accelerators but in space by modern telescopes like NASA's James Webb Telescope. Red Baron published two blogs dealing with new findings on dark matter and dark energy.

Recently, for a change, it was not the US James Webb Telescope but the European Euclid space telescope that made a spectacular observation. By chance, it discovered a "perfect" Einstein ring.

© ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, T. Li
Click to enlarge

This wide-field image shows the ring of exceptional clarity surrounded by an extended stellar halo of the galaxy NGC 6505. In the photo's foreground are colorful stars, and further galaxies decorate the background.

According to the general theory of relativity, Einstein rings are created by the deflection of light from distant galaxies by the gravitational fields of nearer galaxies in front of them.

The deflection of light by masses, as predicted by Albert Einstein, was first observed during a solar eclipse on May 29, 1919. The observed deviation of around 1.75 seconds of arc followed the prediction. Since then, many experimental observations have confirmed the general theory of relativity.

Massive objects in space bend and focus light like a lens. The gravitational force is strong for very massive galaxies and galaxy clusters. These powerful lenses allow astronomers to see the light from very distant galaxies that would be hidden from those lying before them. If the alignment is correct, the light from a distant galaxy forms an Einstein ring around the galaxy in the foreground.

Magnification of the center showing the Einstein ring in all its beauty
          © ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, T. Li

The NGC 6505 galaxy is about 590 million light-years from Earth - a stone's throw away in cosmic terms - and the ring is formed from the light of a previously unknown galaxy - that has not yet a name - at a distance of 4.42 billion light-years.

Ultimately, the Euclid space telescope, which can detect galaxies out to 10 billion light years, is expected to find about 100,000 strong gravitational lenses. Its mission is to map over a third of the sky and create the most extensive cosmic 3D map ever made.

By exploring the expansion and formation of the universe throughout its cosmic history, Euclid will learn about the role of gravity. This will allow astronomers to infer the large-scale distribution of dark matter and reveal the influence of dark energy. This mysterious force is accelerating the expansion of the universe.
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