Supernova Shock Wave May Have Triggered Solar System Formation
Supersonic Shock Wave Heats Gas Ring Around Supernova 1987A - Credit: NASA, P. Challis, R. Kirshner (Harvard-Smithsonian Center for Astrophysics) and B. Sugerman (STScI)
Current scientific explanation for the formation of our solar system begins with a supernova. Why not? We know that most elements come from supernova explosions.
So, it stands to reason that a shock wave generated by this cataclysmic event is quite possibly the hand that set the creation in motion. Theoretically, the shock wave planted material into a cloud of dust and gas – one which eventually collapsed to form the Sun and attending planets. Now new research from Carnegie’s Alan Boss and Sandra Keiser enlightens us even further by providing the first fully three-dimensional models of how it may have happened.
The evidence starts with meteorites. Buried inside these “time capsules” are traces of short-lived radioactive isotopes, or SLRIs. These are types of elements which contain the same number of protons, but a different number of neutrons. Located in primitive meteorites, SLRIs decay over millions of years creating different “daughter” elements. When scientists find these offspring in meteorites, the are broken into specific patterns which means the SLRIs had to have been present before the meteorite itself was formed.
Herein is the mystery… For this to have happened, the SLRIs had to have originated in a supernova event and become part of the pre-solar nebula. From there, they would have been trapped into meteoritic particles in an event which happened in less than a million years.
However, an explanation isn’t just that easy. The relevant traces of the daughter elements aren’t the ones that were injected into the solar nebula. They came from different mineral phases which correspond with the abundances of a stable isotope of the parent element. How do we know this? Each element shows a specific chemical behavior during its formation as a solid. Because the daughter elements match up with the parent elements, it shows they had to have originated from the decay of an unstable parent after the solid had crystallized.
Only iron-60 is created in large quantities by nuclear reactions in massive stars. This means that iron-60 must have been the by-product of another giant star known as an AGB. Boss and Keiser’s previous modeling placed a supernova event as the precursor to the solar system’s formation. Why? Because AGB star shocks are too thick to inject iron-60 into a debris cloud and supernova shocks are significantly thinner.
Supernovae result from the explosive death of a star and are classified as two types
“We’ve had chemical evidence from meteorites that points to a supernova triggering our Solar System’s formation since the 1970s,” remarked lead author, Carnegie’s Alan Boss. “But the devil has been in the details. Until this study, scientists have not been able to work out a self-consistent scenario, where collapse is triggered at the same time that newly created isotopes from the supernova are injected into the collapsing cloud.”
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To take the research to the next level, Boss and Keiser created new models in 3-D. This new method shows the supernova shock wave ramming into the gas cloud. It becomes compress and forms a parabolic shock front which encircles the cloud. This, in turn, creates funnel shaped indentations in the cloud surface and drives the SLRI particles into place. Less than 0.1 million years later, the cloud collapses and the core of a protostar is born… the beginning of the Sun and eventually the planets. According to this new 3-D model, only one or two of the funnels may have been responsible for the SLRI pollution found in primitive meteorites.
“The evidence leads us to believe that a supernova was indeed the culprit,” said Boss. As tidy as the explanation seems to be, there is still more modeling that needs to be done… such as finding the perfect combination of shock wave and cloud patterns which match observations of exploding supernova. “This is the first time a detailed model for a supernova triggering the formation of our solar system has been shown to work,’’ concludes Boss. “We started with a Little Bang 9 billion years after the Big Bang.”
Original Story Source: Carnegie Institution of Science News Release.
