Stars are thought to form in huge filaments of molecular gas. Areas where one or more of these filaments converge, known as hubs, are where massive stars form.
These massive stars, located nearby, would have put the early solar system in danger of a powerful supernova. This risk is more than just hypothetical; a research team from the National Astronomical Observatory of Japan, led by astrophysicist Doris Arzoumanian, looked at isotopes found in ancient meteorites and found possible evidence of the turbulent death of a massive star.
So why did the solar system survive? The gas in the filament seems to be able to protect it from the supernova and its onslaught of radioactive isotopes. “The host filament may protect the young solar system from stellar feedback, both during star formation and evolution (stellar outflow, wind and radiation) and at the end of their lives (supernovae),” Arzoumanian and her team said in a study recently published. in The Astrophysical Journal Letters.
Signs of a supernova
The meteorites studied by the researchers contained small inclusions, or clumps, in the rock about as old as the solar system. These chunks contain isotopes derived from the decay of short-lived radionuclides (SLRs), which can be generated by supernovae. Although SLRs decay after a few hundred million years, which is nothing in cosmic terms, they still leave behind distinctive isotopes.
The team found particularly high levels of SLR isotopes in the meteorites they examined. From the age of the isotopes, they were able to deduce that the SLRs they once belonged to were present in the early solar system. Supernovae are one SLR source, which could mean our solar system has evaded a supernova, though they could form in other ways.
SLRs from the interstellar medium can already float around in the molecular cloud in which a star forms. The birth of massive stars, which don’t live that long (at least in cosmic terms) and die quickly via supernovae, may be another source of can isotopes produced by highly energetic solar or galactic cosmic rays. All of these sources could possibly explain the existence of SLRs in the early solar system.
While SLRs likely existed in the part of the filament where the Sun and Solar System formed, the meteorite samples contained too much of a particular aluminum isotope for the interstellar medium to be the Solar System’s only SLR source. Cosmic rays, which can convert stable isotopes into radioactive ones, had a better chance of explaining the number of isotopes in the meteorites. However, it would have taken too long for this process to produce the levels of SLRs found in the early solar system.
It is very likely that such high SLR levels could come from very intense stellar winds, which would have occurred during the formation of massive stars, or from what was left after one of the massive stars went supernova.
So why didn’t the supernova disrupt the solar system? It seems that the destructive blow was softened by the molecular gases of the filament in which the sun formed. If the isotopes from those long-dead SLRs really came from a supernova or stellar winds, then the amount passing through the filament gas was enough to match what was suggested by the meteorite findings, but not enough to decimate the solar system. The size of this hypothetical supernova or newborn star is still unknown.
“This scenario may have several important implications for our understanding of the formation, evolution and properties of stellar systems,” the researchers also said in the study.
While there are still some unanswered questions, the scientists suspect that if the clouds of the filament in which the sun and solar system formed were large enough, our star and planets would have easily survived a supernova impact.
The Astrophysical Journal Letters, 2023. DOI: 10.3847/2041-8213/acc849 (About DOIs).
Elizabeth Rayne is a creature that writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. When she’s not writing, she’s altering, drawing, or cosplaying as a character she’s never heard of before. Follow her on Twitter @quothravenrayne.