Radio telescopes have spotted a curious alignment of black holes. Several black holes, 7 billion light-years from Earth, seem to be spinning and pointing in the same direction.
South African researchers discovered that this alignment extends over 60 million light-years across, but they are still not exactly clear how it formed. The astronomers looked at 65 radio galaxy jets and noticed that a large fraction of them were aligned along a filament of about 1°. They looked at the probability of this being a random event and found a less than 0.1 percent chance of it.
“Since these black holes don’t know about each other, or have any way of exchanging information or influencing each other directly over such vast scales, this spin alignment must have occurred during the formation of the galaxies in the early universe,” Professor Andrew Russ Taylor, principal author of the study, said in a statement.
In the instants after the Big Bang, the universe went through a phase of exponential growth called cosmic inflation. As the universe expanded, primordial quantum fluctuations were stretched to macroscopic scales; these fluctuations generated small differences between the distribution of matter in the universe, and over time they grew into what we see in the cosmos today – the so-called cosmic web.
The cosmic web indicates that galaxies are distributed in clusters with filaments stretching between them and large voids around them. Within the web, according to the main theories of cosmology, galaxies can be aligned as they please, so this finding was clearly not expected.
The paper, published in the Monthly Notices of the Royal Astronomical Society, suggests potential explanations for this phenomenon. For example, a cosmic magnetic field could push the black holes, and their jets, to align; another explanation includes fields associated with exotic particles, or even peculiar cosmic strings as the cause for the alignment.
The finding was a surprise for the astronomers. The goal of the investigation was to look at the faintest radio sources in the universe, laying the groundwork for the next generation of radio observatories like MeerKAT and the Square Kilometer Array.
“We’re beginning to understand how the large-scale structure of the universe came about, starting from the Big Bang and growing as a result of disturbances in the early universe, to what we have today,” says Professor Taylor, “and that helps us explore what the universe of tomorrow will be like.”