Astronomers Find Quasars Are "Aligned" Across Billions Of Light-Years
November 21, 2014 | by Janet Fang
photo credit: Artist's impression showing schematically the mysterious alignments between the spin axes of quasars (white) and the large-scale structures (blue) that they inhabit. The rotation axes of the quasars’ black holes are indicated with a line / ESO/M. Kornmess
Quasars separated by billions of light-years are lined up in a mysterious way. Astronomers looking at nearly 100 quasars have discovered that the central black holes of these ultra-bright, faraway galaxies have rotational axes that are aligned with each other. These alignments are the largest known in the universe.
Quasars are some of the brightest things known, and at the center of these super luminous nuclei of galaxies are very active supermassive black holes. The black hole is surrounded by a spinning disc of extremely hot material, which gets spewed out in long jets all along the quasar’s axis of rotation.
Using the European Southern Observatory’s Very Large Telescope in Chile, a team led by Damien Hutsemékers from the University of Liège in Belgium studied 93 quasars known to form huge groupings. We’re seeing them now at a time when the universe was only about a third of its current age. “The first odd thing we noticed was that some of the quasars’ rotation axes were aligned with each other—despite the fact that these quasars are separated by billions of light-years,” Hutsemékers says in a news release.
So the team wanted to find out if the rotation axes were linked at that time—and not just to each other, but also to the structure of the universe on large scales. When looking at the distribution of galaxies on scales of billions of light-years, astronomers have found that galaxies aren’t evenly distributed: They form a web of filaments and clump around huge galaxy-scarce voids. This arrangement of material is known as the large-scale structure.
The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarization of the light from each quasar and found a significantly polarized signal for 19 of them. The direction of this polarization helps to deduce the angle of the disc and the direction of the spin axis of the quasar.
These new findings indicate that the rotation axes of quasars tend to be parallel to the large-scale structures that they inhabit. That means that if the quasars are in a long filament, then the spins of their central black holes will point along the filament. (See the image above.) According their estimates, there’s only a one percent probability that these alignments are simply the result of chance.
“A correlation between the orientation of quasars and the structure they belong to is an important prediction of numerical models of evolution of our universe,” says study co-author Dominique Sluse of the Argelander-Institut für Astronomie in Bonn, Germany. “The alignments in the new data, on scales even bigger than current predictions from simulations, may be a hint that there is a missing ingredient in our current models of the cosmos.”
The findings were published in the journal Astronomy & Astrophysics this week. Here’s a detailed simulation of the large-scale structure centered on a massive galaxy cluster. The distribution of dark matter is shown in blue, the gas distribution in orange. The region shown is about 300 million light-years across.
Images: ESO/M. Kornmesser (top), Illustris Collaboration (middle)
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