Our universe is filled with distant supermassive black holes that feed on surrounding gas and dust, emitting bright gamma-ray radiation. A new study explores how many of these show periodic patterns in the variations of their high-energy light.
Putting on a Show
At the center of every galaxy lies a supermassive black hole of millions to billions of solar masses. Many of these — like the Milky Way’s own Sagittarius A* — are quiet, largely invisible lurkers. But some are considerably more attention-seeking, actively accreting material, spewing out winds and jets, and emitting radiation that spans the electromagnetic spectrum.
These active galactic nuclei (AGNs) show variability in their light curves on many different timescales — and a few have been caught flickering in a regular pattern.
Why the Patterns?
Artist’s impression of supermassive black holes that have formed a binary as they’ve sunk to the center of their merged galaxies. [NAOJ]There are lots of potential explanations for periodic variability in an AGN’s light curve. The black hole may host powerful jets that precess about an axis, driving a lighthouse effect in their emission. The flow of accreting material onto the black hole might wax and wane periodically. And in some ...