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Science & Tech.
Pradeep Kumar

09/04/21 09:00 AM IST

Kaleidoscopes in the sky

In news

A group of astronomers have discovered a dozen quasars that have been warped by a naturally occurring cosmic "lens" and split into four similar images.

Details
  • Quasars are extremely luminous cores of distant galaxies that are powered by supermassive black holes.
  • This rare discovery increases the number of known quasars or quads by about 25% and can help determine the expansion rate of the universe and help address other mysteries.
Background
  • Quadruply imaged quasars are rare, and the first quadruple image was discovered in 1985.
  • Over the past four decades, astronomers had found about fifty of these “quadruply imaged quasars” or quads for short, which occur when the gravity of a massive galaxy that happens to sit in front of a quasar splits its single image into four.
Quads
  • The quads are gold mines for all sorts of questions.
  • They can help determine the expansion rate of the universe and help address other mysteries, such as dark matter and quasar 'central engines
Cosmological Dilemma
  • In recent years, a discrepancy has emerged over the precise value of the universe's expansion rate, also known as Hubble-Lemaître’s constant.
  • Two primary means can be used to determine this number: one relies on measurements of the distance and speed of objects in our local universe, and the other extrapolates the rate
  • from models based on distant radiation left over from the birth of our universe called the cosmic microwave background.
  • The problem is that the numbers do not match. The quasars lie in between the local and distant targets used for the previous calculations.
  • The new quasar quads, which the team gave nicknames such as "Wolf's Paw" and "Dragon Kite," will help in future calculations of Hubble-Lemaître’s constant and may illuminate why the two primary measurements are not in alignment.
  • "Machine learning along with Augmented Intelligence (AI) tools was key to our study, but it is not meant to replace human decisions," explains Krone-Martins, Lecture at University of California.
Source: PIB

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