The violent event that likely preceded the formation of our solar system offers the solution to a long-standing meteorite mystery, says new work by Carnegie’s Alan Boss, published in The Astrophysical Journal†
The raw material that made up our solar system was scattered when the shock wave from an exploding supernova injected material into a cloud of dust and gas, causing it to collapse on its own. In the aftermath of this event, most of the injected matter was pulled by gravity toward the center of the whirlwind, where the intense pressure build-up allowed nuclear fusion to begin with, and the sun was born. The young star was surrounded by a rotating disk of the remaining gas and dust, from which the planets and other solar system bodies – some of which eventually disintegrated to form asteroids and meteorites – fused.
“The mystery comes from studying the isotopic composition of meteorites, which can be used as a laboratory to test theories about the formation and evolution of the solar system,” Boss explains.
Isotopes are versions of elements that have the same number of protons, but a different number of neutrons. Sometimes, as is the case with radioactive isotopes, the number of neutrons present in the nucleus can make the isotope unstable. To gain stability, the isotope releases energetic particles, which change the number of protons and neutrons, and transmutes it into another element called a daughter isotope.
Boss added: “Because we know exactly how long this process takes for different radioactive isotopes, measuring the amount of daughter products in meteorites can tell us when and possibly how they formed.”
For example, the iron isotope with a atomic weight of 60 is only produced in significant amounts by a supernova explosion and it takes 2.6 million years for half of the atoms to decay — the so-called “half-life” — to its daughter isotope, cobalt-60. So, when significant amounts of cobalt-60 are found in primitive meteorites called carbonaceous chondritesThis tells researchers that the raw material from which the chondrite was built contained the remains of a supernova explosion that occurred just a few million years prior to its formation.
The chondrite record can be used to confirm the story about the origin of the supernova for our solar system. But other, less primitive, non-carbonaceous meteorites lack this iron-60 composition, meaning the material from which they formed did not come from a stellar explosion. So, where did it come from?
“No physical explanation has been given for this dramatic change,” Boss said.
He has refined models of our solar system‘s formation over several decades and was one of the founders of the story of the origin of supernova injections. By extending the time period reflected in his simulations, he was able to show that after the collapse that supplied the chondrites with iron-60, the supernova’s shock front interstellar dust past the resulting disk and accelerate the resulting protostar to a speed of several kilometers per second. This is enough to cause the young sun to encounter a new patch of interstellar material depleted in iron-60 and other supernova-generated materials. isotopes within a million years.
“After working on the problem of supernova “It was great to finally link this model to the meteoric evidence,” Boss concluded. “It closes this story with a neat bow.”
Alan P. Boss, Possible implications of relatively high levels of initial 60Fe in iron meteorites for the non-carbonaceous-carbon meteorite dichotomy and solar nebula formation, The astrophysics magazine (2022). DOI: 10.3847/1538-4357/ac6609
Carnegie Institute of Science
Quote: Unraveling a Meteorite Mystery Reveals the Solar System’s Origin Story (June 2022, June 29) retrieved June 29, 2022 from https://phys.org/news/2022-06-unraveling-meteorite-mystery-reveals-solar.html
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