Astronomers said on April 6, 2021, they have seen two rare double quasars. Each pair is believed to reside in the middle of two merging galaxies in the very distant universe. Astronomers estimate that only one in 1,000 quasars is double that, so finding two double quasars can be considered lucky. However, the astronomers would tell you they weren’t taking advantage of luck. They used a series of telescopes to guide them from step to step, in a methodical unraveling of the mystery of which the bright, apparently single quasars might actually be double. As lead researcher Yue Shen of the University of Illinois at Urbana-Champaign put it:
Finding these double quasars is like finding a needle in a haystack.
A collaboration between scientists and some of the best telescopes in the world resulted in new images of the double quasars. The study was published in the peer-reviewed journal on April 1, 2021 Nature astronomy
To find the quasar pairs, astronomers studied 3D maps from the Sloan Digital Sky Survey to find candidates with double quasar. They then used data from the Gaia Observatory to determine the locations. Gaia can detect slight fluctuations in the motion of the distant quasars. Since quasars vary in brightness depending on how much material the black hole is currently consuming, they produce a slightly flickering appearance. The scientists compared the varying brightness between the quasar pair, as seen in the video above, to that of the double flashing lights on a railroad crossing. Finally, the team of scientists used the Hubble Space Telescope to image four candidates, two of which turned out to be close pairs of quasars.
The video simulation above shows the brilliant, flickering light of a pair of quasars. Astronomers concluded that the flashing light is a telltale sign of the presence of two quasars and not a single object.
Each of the two newly discovered pairs of quasars – or four total quasars – were discovered within 10,000 light-years of their partner. That’s very close on a cosmic distance scale; In comparison, our Sun is about 26,000 light-years from the supermassive black hole at the center of our Milky Way Galaxy.
A quasar is an object in the distant universe that produces enormous amounts of energy. Quasars have such an amazing brilliance that they can be seen all over the universe. So we see them at a time when the universe was young, and so they can help reveal conditions in the early cosmos. Quasars are thought to lie in the hearts of young galaxies in the early universe. The energy of a quasar is believed to be created when a supermassive black hole furiously feeds on incident matter. The light from these two quasar pairs comes to us from a time when the universe was about 10 billion years old. If we could see them today as they are now, we could discover that each quasar pair has merged into a new giant black hole.
More than 100 double quasars are known, but none are as far in space or as far back in time as these new pairs. Scientists hope the discoveries will provide a new way to investigate collisions between galaxies and the merging of supermassive black holes in the early universe. Johns Hopkins University team member Nadia Zakamska said:
This really is the first example of double quasars at the height of galaxy formation that allows us to explore ideas of how supermassive black holes converge to eventually form a binary number.
As these distant galaxies begin to merge and the gas from gravitational distortions sends material in, the quasars shoot up. The radiation from the quasar will eventually drive winds that sweep the inner part of the galaxy free of gas and dust. This creates a shortage of star-forming material, and as star formation stops, the galaxies settle into their elliptical shape.
Zamaska explained the importance of this discovery:
Quasars have a profound influence on the formation of galaxies in the universe. Finding double quasars in this early era is important because we can now test our ancient ideas of how black holes and their host galaxies evolve together.
View bigger. On the left is quasi pair J0749 + 2255, imaged by the Hubble Space Telescope on January 5, 2020. On the right is quasi pair J0841 + 4825, imaged by Hubble on November 30, 2019. dwellings are too dim to be seen with a current telescope. Image via NASA / ESA.
This artist’s concept depicts 2 strikingly bright quasars and the merging galaxies in which they reside. Both quasars have supermassive black holes at their core. A new study suggests that as the 2 galaxies merge and the quasars get closer together, the 2 black holes will merge to form an even heavier black hole. Image via NASA / ESA / J. Olmsted / STSci.
One day, a double quasar and galactic amalgamation, as scientists have seen far in the universe, will occur much closer to home. Our Milky Way Galaxy and the adjacent Andromeda Galaxy are on a collision course. Several billion years from now, as our two galaxies interact and pull material apart, the currently silent supermassive black holes in the centers of the galaxies will catch fire. The falling material will illuminate the quasars and create two dazzling spotlights that shine in our night sky as bright or brighter than a full moon. The radiation from the quasars will sterilize planets and destroy all civilizations at your fingertips.
Bottom Line: Scientists recently released Hubble images of the farthest and oldest known pairs of quasars in merging galaxies.
Source: A hidden population of high redshift double quasars revealed by astrometry
Via Hubblesite
