Einstein Ring

What is the Einstein ring?

• An Einstein ring, also known as an Einstein–Chwolson ring or Chwolson ring is a ring of light created when light from a galaxy, star or other light-emitting cosmic objects passes near a massive object before it reaches the Earth, or in this case.
• When this happens, gravitational lensing causes the light to get diverted and if the source, lens and the observing element are all in perfect alignment, this light appears as a ring. 
• This particular example was formed from the light of a distant galaxy SPT-S J041839-4751.8, which is around 12 billion light-years away from our planet, which also makes it one of the oldest galaxies in the universe.
• From Webb’s point of view, this galaxy is positioned directly behind another galaxy that is so massive that its gravitational pull warps space and time. 
• The blue object in the centre of the ring is this foreground galaxy. As the light from the background galaxy travels to the Webb telescope, it has to cross the warped space-time near the foreground galaxy. This is what makes the light appear like a curved ring.

Note: 

• Gravitational lensing is predicted by Albert Einstein’s theory of general relativity. Instead of light from a source travelling in a straight line (in three dimensions), it is bent by the presence of a massive body, which distorts spacetime. 
• An Einstein Ring is a special case of gravitational lensing, caused by the exact alignment of the source, lens, and observer. 
• This results in symmetry around the lens, causing a ring-like structure.

About  James Webb Space Telescope-

• The $10 billion telescope is a space telescope is a joint venture of NASA, European Space Agency (ESA), and the Canadian Space Agency.
• It was launched on 25 December 2021 on an Ariane 5 rocket from Kourou, French Guiana, and arrived at the Sun–Earth L2 Lagrange point in January 2022. 

• It succeeded the Hubble Space Telescope as NASA’s flagship astrophysics mission.

• It will observe in near-infrared light rather than light in the visible part of the spectrum (unlike Hubble) and thus it will have a much greater capacity to see obscure stars and galaxies.
• Webb has two primary scientific missions, which together will account for more than 50 percent of its observation time. 
  • First, explore the early phases of cosmic history, looking back in time to only a few hundred million years after the Big Bang.
  • Its second major goal is the discovery of exoplanets, meaning planets outside the solar system. It will also investigate the potential for life on those worlds by studying their atmospheres.  

• It was formerly known as the “Next Generation Space Telescope” (NGST) and it was renamed in 2002 after a former NASA administrator, James Webb.

Further reading: https://journalsofindia.com/james-webb-telescopes-first-images/