In News:

• The European Space Agency’s (ESA) Euclid space telescope has recently discovered a rare Einstein ring around the galaxy NGC 6505, located nearly 590 million light-years from Earth.
• This ring was formed by the light of a distant unnamed galaxy situated 4.42 billion light-years away, distorted and amplified due to gravitational lensing by NGC 6505.

What is an Einstein Ring?

• It is a circular ring of light that appears around a massive celestial object such as a galaxy, dark matter concentration, or cluster of galaxies.
• Caused due to strong gravitational lensing, it occurs when a massive foreground object (gravitational lens) bends and amplifies the light from a background object, resulting in a circular or arc-like appearance.
• The phenomenon only results in a full ring when the observer, lensing object, and background galaxy are almost perfectly aligned.

Theoretical Basis

• Named after Albert Einstein, who in his General Theory of Relativity predicted that massive objects warp space-time, thereby bending the path of light.
• The phenomenon of gravitational lensing, and by extension Einstein rings, was first theoretically anticipated by Einstein and empirically confirmed much later.

Scientific Importance

• Extremely rare phenomena: Occur in less than 1% of galaxies.
• Serve as natural cosmic magnifying lenses that allow scientists to study:
  • Dark Matter: Helps trace the invisible distribution of dark matter through gravitational effects.
  • Dark Energy: Supports understanding of dark energy’s role in accelerating the universe’s expansion.
  • Distant Galaxies: Reveals otherwise invisible galaxies by amplifying their light.
  • Universe Expansion: Provides data on how space between galaxies stretches over cosmic time.

Gravitational Lensing: Explained

• Gravitational lensing occurs when a massive body (galaxy, cluster, black hole) creates a gravitational field that bends and magnifies light from objects behind it.
• This leads to multiple outcomes — arcs, double images, or full rings (Einstein rings).
• The lensing object in the recent case is NGC 6505, a galaxy first observed in the 19th century.

Observation and Imaging

• Einstein rings are not visible to the naked eye and require powerful space telescopes like Euclid for detection.
• Euclid captured images showing a bright central galaxy (NGC 6505) with a distinctive, cloudy ring formed by the bent light from the background galaxy.

About the Euclid Space Telescope

• Launched in 2023 by ESA using a SpaceX Falcon 9 rocket from Cape Canaveral, Florida.
• Operates from Lagrangian Point 2 (L2), located 1.5 million km from Earth.
• Designed for a six-year mission to study the dark universe.
• Key Objectives:
  • Create the largest 3D map of the cosmos.
  • Observe billions of galaxies across 10 billion light-years.
  • Understand the distribution of dark matter and the influence of dark energy in the early universe.
  • Study light emitted from galaxies up to 10 billion years ago to trace cosmic evolution.