Astronomers discover 12 rare quadruple quasars that can better tell rate of universe expansion


A group of international astronomers has discovered 12 rare quasars, each offering four distinct quadruple images, commonly called Einstein’s cross. This discovery could help refine the existing understanding about our universe’s rate of expansion and unravel mysteries surrounding dark matter.

Scientists from the Gaia Gravitational Lenses Working Group (GraL), which included PhD student Priyanka Jalan from India, combined multiple telescope observations to confirm this discovery.

The first quadruple quasar image was captured in 1985 and since then, only 50 such quasars have been identified. The latest finding has now increased the total confirmed Einstein’s crosses by 25 per cent.

Quasars are distant galaxies with extremely luminous nuclei. They consist of black holes, measuring many million times larger than our Sun, surrounded by thick gaseous matter. Quasar observations are mainly used to study dark matter in determining the evolution of galaxies and to understand the rate of expansion of our universe, which is measured using the Hubble-Lemaítre constant.

“There are two ways of calculating the Hubble-Lamaítre constant, but both values do not match, thus creating a discord. More discoveries of such quasar quadruples can help resolve this, thereby helping accurately calculate the rate at which our universe is expanding,” said Jalan, who is a final year PhD student at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital.

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Along with senior scientist Jean Surdej, a Belgium-based visiting astronomer to ARIES, Jalan was involved in data analysis of a large number of images which were captured using multiple telescopes and during the European Space Agency’s (ESA) sky surveys in the last 18 months. Big Data and Augmented Intelligence was applied to confirm this rare discovery.

Gravity causes massive objects like galaxies and emissions from them to bend over time and space. Similarly, emissions from a quadruple quasar are said to pass through such deflection causing ‘natural’ lenses. Some deflection is resultant of the presence of numerous galaxies acting as barriers located between a source and Earth, ultimately splitting it into four images.

“We needed to confirm that the four closely packed images were not a pure chance alignment of four independent sources, but really four images of a single, distant source, lensed by an intervening galaxy,” Gaia team member Christine Ducourant of the University of Bordeaux in France and co-author of the research published in The Astrophysical Journal, said in an ESA statement.

The closest quadruple quasar, Jalan reported, among the twelve newly identified was located 5,000 mega parsecs away.

In fact, researchers at ARIES have already started newer quasar observations using the institute’s own 3.6m Devasthal Optical Observatory (DOT).

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