The Hindu: Published on 3rd March 2025:
Why in News?
The Euclid space telescope, launched by the European Space Agency (ESA), has discovered an Einstein ring in the galaxy NGC 6505, located 590 million light-years away. Named Altieri’s ring, this discovery is unique because it has been found in a well-studied nearby galaxy, making it a rare and valuable find.
Understanding the Discovery
What is an Einstein Ring?
Predicted by Albert Einstein in his General Theory of Relativity (1915).
When light from a distant galaxy passes near a massive object (like another galaxy), the object’s gravity bends the light, forming a ring-shaped image known as an Einstein Ring.
It occurs only when the distant galaxy, foreground lens, and Earth are almost perfectly aligned.
Why is Altieri’s Ring Special?
It is one of the few known Einstein rings in a nearby galaxy.
Only five other such gravitational lenses have been discovered at similar distances.
The ring is formed by the distorted images of a galaxy 4.5 billion light-years away.
The discovery proves that even old, well-known galaxies can yield new insights when observed with advanced telescopes.
How Was the Discovery Made?
September 2023: Bruno Altieri, an ESA astronomer, noticed a blurry image of the ring in Euclid’s test data.
The image was unfocused because Euclid was still being calibrated.
March 2024: Follow-up observations using the Keck Cosmic Web Imager (KCWI) and other telescopes confirmed the Einstein Ring’s nature.
Scientific Importance of Einstein Rings
- Proving General Relativity: They confirm Einstein’s prediction that gravity can bend light.
- Studying Dark Matter: Dark matter bends light but remains invisible—Einstein rings help measure its effects.
- Measuring Cosmic Expansion: The light distortion helps calculate the universe’s expansion rate.
- Observing Distant Galaxies: Gravitational lensing allows astronomers to study galaxies that would otherwise be too faint to see.
Role of Euclid Space Telescope
Launched in July 2023, Euclid’s mission is to map the dark universe.
It will help detect 100,000 gravitational lenses, but Einstein rings as close as Altieri’s Ring are rare.
Euclid’s early success proves its capability to advance cosmology and astrophysics.
What Happens Next?
- Euclid will continue scanning the sky, looking for more gravitational lenses.
- Astronomers will use Altieri’s Ring to further study dark matter and cosmic evolution.
- Future discoveries could refine our understanding of spacetime curvature and galactic structures.
Key Takeaways
- The Euclid Space Telescope has discovered Altieri’s Ring, a new Einstein Ring in NGC 6505.
- The ring confirms Einstein’s General Relativity and helps study dark matter and cosmic expansion.
- Euclid is expected to discover 100,000 gravitational lenses, but nearby rings like this are extremely rare.
- This discovery highlights the importance of advanced telescopes in revisiting known galaxies for new insights.
