Supernova trigger

Well, our Sun takes about 30 million years to incubate as a protostar and form a mature sun. Stars three times the mass of our Sun might take just a million years to be born, and stars one tenth the size of our Sun might emerge in about 100 million years. Protostars are just dense clouds of gas and dust. Remember, a supernova triggers their gravitational collapse into a star (figures 7.2 and 7.3). 

Wasserburg G. J., GMhnoR., and Busso M. (1998) A test of the supernova trigger hypothesis with Fe-60 and Al-26. Astrophys. J. 500, L189—L193. 

In 1960 Fred Hoyle and William Fowler discovered that thermonuclear combustion in the dense core of a degenerate star (the word degenerate is used in the sense of quantum theory and will be made exphcit later) could trigger the explosion and volatilisation of the star. If we add the idea that post mortem light emissions are fuelled by the gradual disintegration of an unstable radioactive isotope, nickel-56, a subject to be discussed in great detail later, we obtain the universal explanation of what are now known as type la supernovas. 

Each star follows a different path and at a different rate. Ageing stars turn red, except for the most massive, which become violet or even ultraviolet, gradually moving away from the main sequence. Their core temperatures and pressures increase, thereby triggering further nuclear reactions which can build carbon from helium as the stars ascend the giant branch. The construction of nuclear species in massive stars reaches its apotheosis in the explosion of type II supernovas. 

These elements are scattered throughout the universe when massive stars end their lives. When there is no fuel left to burn, the core collapses once again, and there is nothing to stop it. A shock wave from this collapse causes a rebound that fuels an enormous explosion a supernova. The outer layers of the star are blown out into space, and the energy that is released triggers new nucleosynthesis reactions, which make the heavy elements beyond bismuth - up to uranium, and at least a little beyond. 

Another idea under investigation can be labeled self enrichment of the molecular cloud. The idea uses the observation that in a giant molecular cloud, serial star formation may occur, where the massive stars in the first batch of stars to form explode as supernova and trigger a second round of star formation, the massive stars of which explode and trigger yet another round of star formation. As each supernova explodes, it dumps short-lived nuclides... 

An object which is about 300 light years in diameter and which closely resembles the terminal stage of a supernova explosion is visible today in the constellation Orion (the Orion Halo). A number of very bright young stars are located within the Orion Halo, and their ages are estimated to be less than 5-10 million years obviously their formation was triggered by the shock wave of the supernova explosion. 

A related question is this Which types of stars or supernova explosions produce the extinct radioactive nuclei thatare found in the solar system Here the reader is referred to the entry for each specific isotope. But this much must be appreciated first. Some radioactivities appear to be made primarily by the thermonuclear explosions of white-dwarf stars, called Type la supernovae. Others are created primarily in massive stars whose cores collapse to become neutron stars to initiate an explosive ejection (Type II supernovae). Type II supernovae occur three to five times more frequendy than do Type la supernovae. Some radioactive nuclei are made within differing portions of each event, some prior to the ejection, but some during the heat of the ejection process. And still other radioactive nuclei are created within evolved stars that do not become supernovae (red giants). This diversity of origin renders uncertain the identity of those extinct radioactivities that are to be attributed specifically to that supernova thatis supposed to have triggered the formation of the solar system. In recent scientific... 

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