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As astronomers have learned more about the tumultuous and unforgiving nature of the universe, we’ve been comforted to know that there are no stars in our cosmic backyard threatening to go supernova. That wasn’t always the case, though. A new analysis of meteorites suggests that our solar system may have survived a supernova explosion billions of years ago. So, how did the Sun survive?
Today, our solar system is isolated from other stars. The closest star, Proxima Centauri, is 4.2 light-years away. However, stars don’t just pop out of nowhere, they form within molecular clouds where dust and gas slowly coalesce, gaining mass until nuclear fusion begins. Over time, these star-forming regions are consumed, and the stars they create drift apart. The densest parts of these clouds, where multiple filaments of gas intersect, create stars much larger than the Sun. That can be a problem as these objects only last a few million years before they run out of hydrogen and blow their top.
Research from the National Astronomical Observatory of Japan focused on isotopes found in ancient meteorites. These space rocks contained small inclusions (material embedded within a mineral) that dated to the birth of the solar system. The team, led by astrophysicist Doris Arzoumanian, analyzed the inclusions and found evidence of short-lived radionuclides (SLRs) that might have come from a supernova. These materials decompose in a few million years, but they leave stable decay products that can still be detected today, reports Ars Technica.
The Sun may formed in a molecular cloud similar to Rho Ophiuchi, which is 460 light-years away.
Credit: University of Arizona
SLRs can be produced through various processes, and it’s likely there were some SLRs from non-supernova sources in the original molecular cloud that spawned the Sun, but the substances in the meteorite samples had a very particular profile. There was too much aluminum-26 isotope for the SLRs to have simply drifted in from the interstellar medium.
That all supports the idea that a supernova may have happened close to the Sun billions of years ago. Our solar system may have been saved by the very gas that fed the exploding star. The team found the concentration of SLRs to be consistent with a gentle sprinkling rather than a cataclysm. They speculate that the molecular cloud was still dense enough at the time to cushion the solar system. We don’t know the size or location of this hypothetical star, but the Sun may have narrowly escaped destruction, the evidence of which is still floating around in space rocks.
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