In a blog post on its official website, NASA reported that the Hubble space telescope has taken photos of double quasars that are very close to each other. Such binary extragalactic objects are very rare.

"We estimate that in the distant universe, for every 1,000 quasars, there is one double quasar. So finding these double quasars is like finding a needle in a haystack," said lead researcher Yue Shen of the University of Illinois at Urbana-Champaign.

Quasars are extragalactic objects that have stellar images and powerful emission lines with a large redshift in the spectrum. They were first discovered in 1963 as sources of radio emission with very small angular dimensions.

A study of the spectrums of quasars showed that their lines are very strongly shifted towards longer waves. None of the galaxies have shown such a redshift in their spectrum before. The redshift in the spectrums of galaxies is a consequence of their mutual divergence.

The researchers are convinced that the discovery of these quasars offers a new way of probing collisions between galaxies and the merging of supermassive black holes in the early universe.

"This truly is the first sample of dual quasars at the peak epoch of galaxy formation with which we can use to probe ideas about how supermassive black holes come together to eventually form a binary," said research team member Nadia Zakamska of Johns Hopkins University in Baltimore, Maryland.