When giant black holes at the center of galaxies flare up, the whole galaxy actually looks like it's wobbling in the sky.
March 30, 2026
Original Paper
Gaia Sees Blazars Move: Locating Optical Flares Using Astrometry
arXiv · 2603.26662
The Takeaway
By tracking the precise position of light with the Gaia satellite, astronomers found that blazars shift their center of brightness during flares. This allows researchers to pinpoint exactly where these massive energy outbursts occur within a few light-years of the black hole, despite being billions of light-years away.
From the abstract
When blazars flare, their optical position moves. We show this by combining Gaia DR3 proper motions with epoch photometry for blazars with strong optical jet emission. In 60 of 74 sources with significant proper motion, rising flux drives the centroid upstream while fading flux drives it downstream - a near-universal pattern captured by a simple two-component model of constant extended emission and a flaring region. Using this connection, we geometrically localize the optical flares to within <1