Galaxies, like giant whirlpools, sometimes collide and merge. In this chaos, gas compresses, new stars flare up, and a bright radio beacon is born at the very center. Its light — not visible to the eye, but radio waves — pierces through dust and gas like a siren through fog.

For a long time, such beacons were found only relatively close to us — in galaxies whose light took no more than a couple of billion years to reach us. But the new MeerKAT radio telescope in South Africa, resembling a field of 64 giant dishes, has peered deeper. In just 4.7 hours of observations, it caught a beacon from a galaxy whose light has been traveling for 8 billion years. This is the most distant megamaser ever known.

The same beam of radio waves brought a second surprise: a trace of cold hydrogen that absorbs part of the signal, like a window pane slightly muffling street noise. This means there is a gas cloud in front of the beacon — possibly remnants of the very same galaxy collision. Now astronomers know that such beacons can be found at any distance, and the future giant radio telescope SKA will be able to map a whole array of them. It is as if we are learning to listen to the echoes of ancient catastrophes to understand how our universe grew.