Artist’s concept of an edge-on galaxy, with flows of gas suffusing from it. Image via Science in Public.
What flows into a galaxy
On August 30, 2021, astronomers described a process by which clouds of pure hydrogen and helium gas are pulled into galaxies, to be used in the process of making new stars. The stars convert those very simple elements – hydrogen and helium – into more complex elements including oxygen, carbon, and iron. And then the galaxies pump this “exhaust,” as the astronomers called it, out again into intergalactic space. Supernova explosions cause most of the outward flow. In other words, these astronomers said:
… What flows into a galaxy is a lot cleaner than what flows out.
Astronomers Alex Cameron and Deanne Fisher of ASTRO 3D in Australia – a consortium of nine Australian universities, plus international partners – led this research. The team used a new piece of equipment called the Keck Cosmic Web Imager at the W.M. Keck Observatory in Hawaii. The peer-reviewed Astrophysical Journal Letters published the new work on August 30.
So it’s much the same story we’ve known for decades. It’s about elements being forged inside stars and then released via supernovae. ...