If the heavier elements such as Uranium came from a supernova, then this supernova had to sit somewhere right in the middle of the original solar nebula, because although the ejected matter traveled extremely fast by star or planet standard, it was still not fast enough to truly get across the empty space between clusters of stars. Does this mean the supernova was actually birthed and died in the same nebula or at least in the immediate vicinity in a region that is rich in hydrogen? Could the solar system be still in this nebula? What could endow the solar system as a whole with so much momentum that it acquired a different trajectory around the galaxy than its mother nebula, if the solar nebula is in effect no where to be found?


1 Answer 1


The Uranium on Earth did not come from a single supernova. The Earth formed from material that had been enriched by perhaps a billion stars that lived and died before the Sun and solar system were born. That material, enriched by heavier elements, is turbulently mixed within the galactic interstellar medium and is then gathered together to form new generations of stars. The mixing timescale is much shorter than the age of the Galaxy (see for example How can there be 1,000 stellar ancestors before our Sun?)

However, it is possible that one or two local supernovae did imprint a pattern of odd abundances for particularly rare or short-lived (radioactive) isotopes. It is widely believed that an explanation for the inferred high ratio of $^{26}$Al/$^{27}$Al (the former being radioactive with a half-life of less than a million years) in the early solar system, indicates that it was enriched by the ejecta from a nearby supernova. This may suggest that the Sun was born in a cluster of stars that was numerous enough to have contained very high mass stars capable of exploding as supernovae on short timescales.

Finding the solar systems birth place or its siblings is proving to be a difficult (and perhaps impossible) task, given the time that has elapsed and the multitude of effects that act to disperse stars (and their natal gas) on much shorter timescales (see Parent stars of our Sun - Where are its remains?).


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