https://phys.org/news/2026-07-astronome ... alaxy.html
Researchers have obtained the deepest images ever taken of IC 1101 .... The observations confirm it as the largest known galaxy, spanning roughly 520 kiloparsecs, or about 1.7 million light-years, and containing an estimated 3.4 trillion solar masses in stars.
Compare that to our own Milky Way, at about 26-29 kiloparsecs, or 87 400-90 000 lightyears, and 1.15 trillion solar masses. Note that the solar mass here doesn't mean the mass of the stars alone, but the total weigh measured in solar masses. If you take only the stars of IC 1101 and measure them, their mass would be more than the total mass of the Milky Way which would include the planets, dust, gas, dark matter, black holes etc.
The largest galaxies, called brightest cluster galaxies (BCGs), are products of hierarchical galaxy formation. They grow by absorbing smaller galaxies over billions of years .... the team detected eight extensive, faint, asymmetric stellar structures. Two of them line up with known X-ray "sloshing" disturbances in the surrounding hot cluster gas, evidence that the galaxy is still growing through ongoing accretion .... an earlier X-ray study, which identified similar disturbances as the likely signature of a past collision with another galaxy group roughly 2–3 billion years ago.
The Earth has bee around for 4.5-5 billion years, so this big guy has been gobbling up galaxies for over half of Earths lifetime. And still going.
