After a star explodes in a supernova, the remnants can reform into more stars again and again. These subsequent generations could be full of elements heavier than helium that astronomers refer to as metals, which could explain why the cosmos is littered with puzzlingly metal-rich stars.
Supernovae are often thought of as explosions, but in the later stages of their evolution, they slam into particles in the surrounding interstellar medium and begin to implode instead. This creates a dense cloud of gas and dust, enriched with all of the heavier elements that formed within the dying star that produced the supernova. In some areas of the cosmos, many neighbouring stars can go through this process at the same time, creating even larger clouds.
at the Excellence Cluster ORIGINS in Germany and his colleagues calculated what happens within those dense clouds after the implosion. They found that it can create a cyclical effect, where the cloud gets so dense that stars begin to form, and when those stars eventually explode the whole thing starts over again like a phoenix rising from the ashes. Each cycle would take tens to hundreds of millions of years.
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Gas from the interstellar medium also plays a role 鈥� as it flows into the region of the supernova remnant, it adds mass to the mix, allowing more stars to form in subsequent generations. 鈥淔rom one phoenix, you get two phoenixes,鈥� says Romano. This cycle would probably only happen a few times at most because of interference from external objects such as nearby stars, he says.
However, even a few cycles could be enough to explain the unusual stars that astronomers have spotted with far more heavy elements than we would expect from normal star formation processes. Without these cycles, each supernova would pour its metal-enriched dust into interstellar space, where it would be heavily diluted like a drop in the ocean and wouldn鈥檛 contribute much to the formation of metal-rich stars.
鈥淭he fraction of metals in this cloud is 100 to 1000 times higher than if you were to just enrich the whole region that is affected by the supernova,鈥� says Romano. 鈥淚nstead of a drop of water in the ocean, it鈥檚 like a drop of water in a pond.鈥�
The Astrophysical Journal Letters
