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Did our solar nebula from which our solar system emerged come from the Big Bang or was formed some later time after? If it came from stuff left behind by exploding stars from previous generations, how that stuff came to agregate into a nebula if matter blown back by supernovas travels at relativistic speeds? I mean, once something is thrown into space, it doesn't stop until it hits something or get caught gravitationally by some massive object.
The basics ingredients of our solar system come from both supernovae remnants as well as some primordial hydrogen from the big bang. In what ratio, I don't know I'll have to ask one of my astrophysics colleagues. Theoretical calculation on the abundance of elements other that hydrogen right after the big bang show that only the lighter elements such as Deuterium, Helium, Lithium, Beryllium, etc. were formed. Heavier elements only show up after the first stars formed then blew up as supernovae. There are plenty of heavier elements around in our solar system. Our earth is mainly Iron and Silicon. We can even see spectroscopic evidence of metals in the Sun. Its 'Metalicity' is around 1.8% by weight and consists mainly of Iron.
Not all matter coming from a supernova travels at relativistic speeds. There are plenty of neutrinos coming out that travel at the speed of light but the nuclei are mostly non relativistic.
One article I found, http://adsabs.harvard.edu/abs/1989ApJ...338L...9W
, gives the average velocity of Nickel as 1400 km/sec, small potatoes compared with the velocity of light. Combined with collisions and, as you said gravitational attraction, there is no problem for them to aggregate. It takes a long time of course.
(published on 07/23/2011)
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