What is an Einstein Ring?

Context: The European Space Agency’s (ESA) Euclid space telescope has discovered a rare Einstein ring around a galaxy 590 million light-years from Earth.

What is an Einstein Ring?

• An Einstein ring is a rare ring of light that forms due to gravitational lensing.
• Gravitational lensing occurs when a massive celestial object (a galaxy or cluster of galaxies) creates a gravitational field that bends and magnifies the light from a distant object behind it.
• This was predicted by Albert Einstein’s General Theory of Relativity (1915), which stated that gravity can bend light around massive objects.
• The first Einstein ring was discovered in 1987, and though more have been found since, they remain extremely rare.
  • Less than 1% of galaxies are estimated to have an Einstein ring.
• Einstein’s rings are not visible to the naked eye and can only be observed using advanced space telescopes like ESA’s Euclid.

Why Scientists Study Einstein Rings

• Understanding Dark Matter: Dark matter makes up 85% of the total matter in the universe, but it has never been directly observed.
  • Gravitational lensing helps indirectly detect dark matter by observing how light bends around galaxies.
• Studying Distant Galaxies: Some galaxies are too faint to be observed directly. Gravitational lensing magnifies their light, allowing scientists to study galaxies that would otherwise remain hidden.
• Measuring the Expansion of the Universe: The universe is expanding, stretching space between Earth and other galaxies.
  • Einstein rings provide data on how fast galaxies are moving apart, helping refine measurements of cosmic expansion.

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