Free Astronomy Magazine January-February 2015

SPACE CHRONICLES form huge groupings spread over billions of light-years, seen at a time when the Universe was about one 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 qua- sars are separated by billions of light-years,” said Hutsemékers. The team then went further and looked to see if the rotation axes T he impression and the video show schematically the mysterious alignments be- tween the spin axes of quasars and the large-scale structures that they inhabit that observations with ESO’s Very Large Telescope have revealed. These alignments are over billions of light-years and are the largest known in the Universe. The large- scale structure is shown in blue and quasars are marked in white with the rotation axes of their black holes indicated with a line. This scenario is for illustration only and does not depict the real distribution of galaxies and quasars. [ESO/M. Kornmesser] n were linked, not just to each other, but also to the structure of the Uni- verse on large scales at that time. When astronomers look at the distri- bution of galaxies on scales of bil- lions of light-years they find that they are not evenly distributed. They form a cosmic web of filaments and clumps around huge voids where galaxies are scarce. This intriguing and beautiful arrangement of mate- rial is known as large-scale structure. The new VLT results indicate that the rotation axes of the quasars tend to be parallel to the large-scale structures in which they find them- selves. So, if the quasars are in a long filament then the spins of the cen- tral black holes will point along the filament. The researchers estimate that the probability that these align- ments are simply the result of chance is less than 1%. “A correlation between the orienta- tion of quasars and the structure they belong to is an important pre- diction of numerical models of evo- lution of our Universe. Our data pro- vide the first observational confir- mation of this effect, on scales much larger that what had been observed to date for normal galaxies,” adds Dominique Sluse of the Argelander- Institut für Astronomie in Bonn, Ger- many and University of Liège. The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisa- tion of the light from each quasar and, for 19 of them, found a signifi- cantly polarised signal. The direction of this polarisation, combined with other information, could be used to deduce the angle of the accretion disc and hence the direction of the spin axis of the quasar. “The align- ments 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,” con- cludes Dominique Sluse.