A star similar to our Sun but several times heavier sheds its outer layers before dying. The gas expands outward, forming something like onion rings around the star. When the star finally explodes as a supernova, the light of the explosion passes through these rings and illuminates them, like a flashlight shining through layers of fog.
Astronomers observed supernova SN 2024abvb in a galaxy millions of light-years away. The light from the explosion took several million years to reach Earth, and during that time it passed through several gas rings. Each ring left its mark on the spectrum — the rainbow into which light is split. From these marks, it is clear that the rings consist of helium, carbon, and oxygen and are moving at different speeds, from 150 to 2000 kilometers per second.
The most surprising thing: they found traces of hydrogen in the spectrum, which is usually absent in such supernovae. The hydrogen was located far from the star, in the outermost ring. It seems the star shed its hydrogen envelope long before the explosion, and then, closer to the end, shed helium, carbon, and oxygen.
This picture, several rings with different compositions and tilts, indicates that the star lost material not uniformly but in bursts. Perhaps before the explosion, it pulsated like a heart, ejecting gas in spurts. Such observations help us understand the final days of massive stars.
The gas in the rings reached speeds of 2000 km/s—60 times faster than a rocket traveling to orbit.
In Arthur C. Clarke's novel Rendezvous with Rama, an alien spacecraft passes through a gas cloud, and its light changes — similar to how the supernova's light changed as it passed through the rings.