Black Hole Alignment
Is Not So Mysterious

Andrew Russ Taylor

There’s news of a mysterious alignment of black holes. While that makes for good headlines, the actual scientific findings aren’t so mysterious.¹

The research has just been published in Monthly Notices of the Royal Astronomical Society: Letters, and it looked at the orientation of black hole jets. When black holes consume matter, the heat and pressure of the surrounding accretion disk can throw some of the material away from the black hole at tremendous speed. This material streams away from the black hole forming long trails we call jets. Since these jets always stream away from the poles of a rotating black hole, the alignment of the jets tells us the orientation of the black hole.

The team looked at distant black holes across a 1-degree span of sky, which is about twice the apparent width of the Moon. When they looked at the jets of black holes in this area, they found an apparent alignment. The chance of such alignment occurring randomly is about 0.1%, so it is likely that something caused them to have similar alignments. This is “mysterious” because the black holes are not close enough to each other to be interacting. So there is no way for them to be tugging each other into alignment.

However this kind of alignment is not unexpected. Computer simulations of the cosmos show that intergalactic material should be rotationally aligned along filaments between superclusters. We’ve seen similar alignments among quasars, which is indicative of this large filament structure. So what this work actually shows is further evidence of the large scale filament structure as predicted by computer simulations. The authors are clear to point this out, and don’t claim there is anything mysterious about it.

Unfortunately, “we’ve found further evidence confirming cosmological models” doesn’t garner as many clicks as “Ooh! Mysterious black holes!”