New method could sharpen distance measurements between quasar pairs

By the Everything Space news desk · 18 Sep 2026 · written from the sources below

Image: Phys.org

A technique using light from gas around quasars promises far more precise separation estimates, aiding studies of galaxy mergers and black hole collisions.

Researchers have tested a new way to measure how far apart two quasars actually sit in space when they appear close together in images, addressing a long-standing depth-perception problem in astronomy.

Quasars are extremely bright centers of distant galaxies powered by supermassive black holes. When two appear near each other in the sky, their separation across the sky can be measured precisely, but their separation along the line of sight toward Earth has carried much greater uncertainty, according to the study's lead author, an astrophysicist at the University of Alberta.

Astronomers typically infer distance using redshift, which reflects how fast a galaxy is moving away due to cosmic expansion. But gas near an active supermassive black hole can be pushed outward at high speed, skewing redshift measurements enough to throw off distance estimates by tens of millions of light-years, according to the researcher.

The new approach relies on what is called the quasar proximity effect, which examines gas regions illuminated and heated by a quasar's light. By comparing how these illuminated patches appear for each quasar in a pair, researchers can infer how far apart the two objects truly are, similar to judging the placement of two light sources by where their glow overlaps.

In tests using simulated data, the method narrowed uncertainty in distance measurements to roughly half a million light-years in many cases, a notable improvement over redshift-based estimates.

The technique could let astronomers estimate true separations between quasar pairs without needing additional specialized observations, which can take years to obtain. Understanding these separations matters because it affects estimates of how long it takes two galaxies hosting quasars to merge, eventually causing their central black holes to combine into a larger one.

The researcher plans further work to see how much finer details in quasar light data could improve the method's precision, suggesting the approach merits continued investigation.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.