Astronomers studied the light from 1433 pairs of galaxies, recorded by the DESI instrument. Spectra (the breaking down of light into its colors) revealed that in neighbors lying perpendicular to the disk of a massive galaxy, the gas contains more oxygen. This excess reaches 24% at distances of 30–60 kiloparsecs (about 100–200 thousand light-years). That’s how cosmic cross-pollination works: galactic winds from starbursts blow out heavy elements, which then settle on nearby ‘flowers’.
Why is the flow perpendicular? A galaxy’s disk is packed with dense gas and dust that slow down the wind. But along the minor axis (the short axis), resistance is minimal — a clear corridor. Therefore, metal-enriched gas rushes ‘up’ and ‘down’, into the interstellar medium. At larger distances, the effect vanishes — the wind dissipates. In this way, cosmic cross-pollination turns galaxies into nodes of a shared chemical network.
A metallicity excess of 24% is equivalent to a neighboring galaxy suddenly ‘maturing’ by several hundred million years of evolution, having received a dose of ready-made heavy elements. The oxygen we measure is the ‘ash’ from burnt-out massive stars; in each such neighbor galaxy, there are several million solar masses more of it than in isolated counterparts of the same mass.
The idea of galactic winds carrying chemical elements is reminiscent of ‘panspermia’ on a cosmic scale — except instead of life, they spread the building blocks for planets and future biospheres. In Vernor Vinge’s novel ‘A Fire Upon the Deep,’ civilizations exchange information through a galactic network; here, the galaxies themselves exchange matter, laying the groundwork for chemical evolution.