It is thought that supernova generate cosmic rays, and some of these have really high gamma values. These can be up to γ = 10^9. So potentially cosmic rays should have started arriving very quickly after the first light appeared. The bulk of them were low gamma γ ~ 1.2 or v = .6c or so and arrive later, but there should be some rising flux of cosmic ray particles with decreasing energy.
LC On Sunday, August 1, 2021 at 12:36:19 PM UTC-5 [email protected] wrote: > In the July 16 2021 issue of the journal Science evidence is reported that > 2.5 million years ago a supernova occurred between 160 and 320 light years > from the Earth, and another rather more distant one occurred 6.3 million > years ago. By way of comparison Betelgeuse is 642 light years away. > Although it would've been much brighter than the full moon, that ancient > supernova was not close enough to cause a mass extinction, but it would > have had a noticeable effect on the environment. The x-rays and gamma rays > probably wouldn't have had a major effect but the charged particles emitted > by the supernova that would've arrived about 500 years after the light may > have. The ozone layer would be depleted by at least 7%, and the amount of > ionization in the upper atmosphere would've increased by a factor of 10 and > increase the production of nitrogen oxide compounds by 30%. > > This increase in the production of nitrogen compounds would continue for > at least 5000 years, and these compounds would combine with water and fall > to the earth as rain and act as an excellent fertilizer that would increase > plant growth and so reduce the amount of carbon dioxide in the air and > decrease greenhouse warming. It may have been the cause of the Pleistocene > cooling known to have occurred 2.5 million years ago. Also, when charged > particles from the supernova hit the upper atmosphere they would produce a > heavier version of the electron called a *"muon*" which would be able to > reach the earth surface and even into the ocean to a depth of one kilometer > which would triple the normal radiation level and possibly increase the > cancer and mutation rate. > > The isotope iron-60 has been found in sediments dredged up from the > northern Pacific, it can only be manufactured in the cores of very massive > stars and it has a half-life of only 2.6 million years and decays into > nickel-60. By finding the ratio of these two elements in sediments dredged > up from the northern Pacific scientists determined that the iron-60 must've > arrived on the earth 2.5 million years ago. Iron-60 has even been found in > dust from the moon brought back by Apollo missions. They also found > Plutonium-244 in those ocean sediments and it has a half-life of 80 > million years and decays into uranium 236. The plutonium uranium ratio is > consistent with the 2.6 million year age obtained by the iron nickel > ratio. > > By using the incredibly precise data about the position and velocity of > nearby stars obtained by the Hipparcos satellite, it was determined that > 2.5 million years ago there was a rather dense clump of large stars called > the "*Scorpius-Centaurus OB Association*" less than 300 light years from > the earth. Today that clump contains 79 stars that are large enough to > someday end their life as a core collapse supernova, based on that it is > statistically estimated that in the last 13 million years about a dozen > former members of that clump did indeed end their lives in a supernova. > Today that clump of stars is moving away from us. > > Statistically speaking, a few supernovas must've exploded less than 30 > light years from Earth sometime during its 4.5 billion year history. It > has been hypothesized that a major mass extinction at the end of the > Devonian period 359 million years ago was caused by a supernova that was 60 > light years away or less. > > A nearby supernova 2.5 million years ago > <https://science.sciencemag.org/content/373/6552/269> > > John K Clark > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/857a9881-dd4c-49ff-8df3-87dad70b7424n%40googlegroups.com.
