‘Only 1% of universe’: Why Einstein Ring is one of the rarest phenomena discovered by humans
Produced by Tarun Mishra
Produced by Tarun Mishra
An Einstein ring is a circular appearance of light around a celestial object, caused by gravitational lensing. This occurs when a massive object, such as a galaxy or a black hole, bends the light from a more distant object behind it. The effect, predicted by Einstein’s general theory of relativity, forms a ring when the alignment between the source, lens, and observer is nearly perfect.
ESA’s Euclid space telescope observed an Einstein ring in 2023 around the galaxy NGC 6505, located 590 million light-years from Earth. The light forming the ring originated from a much more distant galaxy, 4.42 billion light-years away. Such discoveries are rare, as Einstein rings appear in less than 1% of observed galaxies.
Dark matter, which constitutes about 85% of the universe’s total matter, does not emit or reflect light, making it undetectable through conventional methods. However, its gravitational effects influence light bending in Einstein rings. Analysing these rings helps scientists study the distribution and properties of dark matter.
Many distant galaxies are too faint for direct observation, but gravitational lensing magnifies their light. By studying Einstein rings, astronomers gain insights into galaxies that existed billions of years ago, improving understanding of early cosmic structures.
The universe is constantly expanding, and gravitational lensing provides a method to measure this expansion. Observing Einstein rings allows scientists to refine calculations of the universe’s growth rate and overall structure.
Detecting Einstein rings requires advanced telescopes like Hubble and Euclid, as they are not visible to the naked eye. Their occurrence is rare, requiring precise alignment between the source, lens, and observer. Most are observed in radio or infrared wavelengths, necessitating specialised instruments.
1. B1938+666 (1998): The first complete Einstein ring observed using the Hubble Space Telescope. 2. SDSSJ0946+1006 (2008): A double Einstein ring, where two background galaxies were lensed by the same foreground galaxy. 3. "Cosmic Horseshoe" (2007): A nearly complete Einstein ring discovered in the Sloan Digital Sky Survey. 4. NGC 6505 (2023): The most recent Einstein ring, captured by ESA’s Euclid telescope.