In a newly observed cosmic event, astronomers using the Very Large Telescope (VLT) and ALMA have witnessed a violent collision between two galaxies, revealing how a quasar's radiation can halt star formation in a merging galaxy. This 'cosmic joust,' as researchers call it, showcases one galaxy blasting radiation into another, disrupting its gas structure.
Published in the journal Nature on May 21, 2025, the study details how a quasar, the intensely bright core of a galaxy powered by a supermassive black hole, acts like a weapon. It shoots radiation into its partner galaxy, interfering with the dense gas clouds necessary for creating new stars. The collision occurs at speeds of 500 km/s.
This marks the first direct observation of a quasar's radiation impacting a regular galaxy's inner gas. The quasar's radiation strips away gas and dust in the companion galaxy, leaving behind only small, dense clumps, which are likely too compact to initiate star formation. This interaction not only damages the companion galaxy but also fuels the quasar's activity as the collision brings more gas to the supermassive black hole.