Supernova explosion

An unknown event disturbed the equilibrium of the interstellar cloud, and it collapsed. This process may have been caused by shock waves from a supernova explosion, or by a density wave of a spiral arm of the galaxy. The gas molecules and the particles were compressed, and with increasing compression, both temperature and pressure increased. It is possible that the centrifugal forces due to the rotation of the system prevented a spherical contraction. The result was a relatively flat, rotating disc of matter, in the centre of which was the primeval sun. Analogues of the early solar system, i.e., protoplanetary discs, have been identified from the radiation emitted by T Tauri stars (Koerner, 1997). 

This is an extremely small quantity, which combined with the also extremely small interaction of gravitational waves (GWs) with matter makes it impossible to generate and detect GW on earth. Fast conversions of solar-size masses are required to produce signals with amplitudes that could be detectable. Astrophysical sources are for instance supernova explosions or a collision of two neutron stars or black holes. 

A GW gives rise to a quadrupolar deformation normal to the direction of propagation. The deformation can be described by means of a dimensionless strain amplitude h = AL/L, where AL is the deformation of a region of space-time separated by a distance L. For example, a supernova explosion, with a mass conversion into GWs of 1% of the total mass, at a distance of 10 kpc (roughly in the centre of our galaxy), would cause a strain on earth of h 3 x 10-18 [50],... 

The interstellar medium is thus a chemically diverse medium fed nearly all of the chemical elements by supernova explosions. Conditions in the interstellar medium produce a cocktail of molecules that ultimately find themselves back on the surface of planets during the formation of the new star and solar system. Does the interstellar medium seed life with molecules from space The nature of interstellar medium chemistry might then add credibility to the formation of life in many places within the Universe and act as a panspermia model for the origins of life. 

Fig. 5.12. Calculated abundances after decay of 56Ni and other radioactive nuclei, relative to solar, in material ejected from a typical Type II supernova explosion, averaged over initial masses 10 to 50 M . Dominant isotopes of each element are circled. Adapted from Tsujimoto (1993).

The site of the r-process is also not clear, but it seems that the conditions needed to reproduce Solar-System r-process abundances may hold in the hot bubble caused by neutrino winds in the immediate surroundings of a nascent neutron star in the early stages of a supernova explosion (see Fig. 6.10). Circumstantial evidence from Galactic chemical evolution supports an origin in low-mass Type II supernovae, maybe around 10 M (Mathews, Bazan Cowan 1992 Pagel Tautvaisiene 1995). Another possibility is the neutrino-driven wind from a neutron star formed by the accretion-induced collapse of a white dwarf in a binary system (Woosley Baron 1992) leading to a silent supernova (Nomoto 1986). In stars with extreme metal-deficiency, the heavy elements sometimes display an abundance pattern characteristic of the r-process with little or no contribution from the s-process, and the... 

Nevertheless, as has been emphasized by Ramaty et al. (2000), the kind of boost to the cosmic-ray flux per supernova implied by Eq. (9.57) is untenable on energetic grounds. From present-day abundances, one can estimate the quantity Q/W, the number of Be atoms per erg of cosmic-ray energy. Given an iron yield of 0.2 M per average supernova (of both types) today, and a Be/Fe ratio of 10-6, one finds a yield of 4 x 1048 Be atoms per supernova. If the typical supernova explosion energy is 1051 erg and the cosmic-ray acceleration efficiency is 10 per cent, this... 

Discovery of the neutron (Chadwick) and positron (Dirac, Anderson). First nuclear reaction induced in an accelerator (7Li(/ , a) Cockcroft and Walton). Baade and Zwicky suggest a neutron star may be created as residue of a supernova explosion. 

In the early thirties of the last century Baade and Zwicky conjectured in their studies of supernova explosions that supemovae represent a transition from ordinary stars to compact objects, whose size is an order of magnitude smaller than the size of a white dwarf. At that time it was already known that the atomic nucleus consists of neutrons and it was clear that the density of the remnant objects must be of the same order as the nuclear density. Baade and Zwicky predicted that a supernova explosions will result in objects composed of closely packed neutrons (neutron stars). Prior to the beginning of the second World War (1939) a number of theoretical works by Landau, Oppenheimer, Volkoff and Snider showed, that indeed objects could exist with sizes about 10 km and masses about a solar mass. The density in these objects is about the nuclear saturation density and they basically consist of neutrons with a small amount of protons and electrons. The studies of neutron stars were subsequently stopped most likely due to the engagement of the nuclear scientists in the development of the nuclear bomb both in the West and the East. 

Speculations about connection of the cosmological GRB with transition from the hadronic to quark star seems to be interesting, because they explain connection between GRB and supernovae explosion, with arbitrary time delay between these events, including very large, exceeding the Hubble time. 

The relativistic EOS of nuclear matter for supernova explosions was investigated recently [11], To include bound states such as a-particlcs, medium modifications of the few-body states have to be taken into account. Simple concepts used there such as the excluded volume should be replaced by more rigorous treatments based on a systematic many-particle approach. We will report on results including two-particle correlations into the nuclear matter EOS. New results are presented calculating the effects of three and four-particle correlations. 

Finally we consider the question whether the effect of diquark condensation which occurs in the earlier stages of the compact star evolution (t 100 s) [8, 21, 22] at temperatures T Tc 20 — 50 MeV can be considered as an engine for explosive astrophysical phenomena like supernova explosions due... 

The scenario which emerges from these findings is the following two-step scenario. The first event is the supernova explosion which forms a compact stellar remnant, i.e. a neutron star (NS) the second catastrophic event is associated with the NS and it is the energy source for the observed GRB. These... 

In our scenario, we consider a purely hadronic star whose central pressure is increasing due to spin-down or due to mass accretion, e.g., from the material left by the supernova explosion (fallback disc), from a companion star or from the interstellar medium. As the central pressure exceeds the threshold value Pq at static transition point, a virtual drop of quark matter in the Q -phase can be formed in the central region of the star. As soon as a real drop of Q -matter is formed, it will grow very rapidly and the original Hadronic Star will be converted to and Hybrid Star or to a Strange Star, depending on the detail of... 

The all-important question would be to know what is life and as per Carl Sagan, the astrophysicist, it is physics as it contains all the elements created by Big-Bang and from supernova explosion of stars and all these are in the domain of physics. 

The brightest X-ray nebulas are the remnants of supernova explosions. The ejecta are thrown out so forcefully that the collision with neighbouring interstellar gases produces temperatures of several million degrees. This is sufficient to emit photons in the keV range. It is no surprise that most X-ray binaries and supernova remnants should be located in the galactic disk. 

S tellar winds and planetary nebulas also play an important role in the chemical economy of our Galaxy, as they probably do in all the others. In particular, they enhance levels of nitrogen, carbon and heavy elements beyond iron (by the s process). For the main part, newly made elements are produced and launched into circulation by the last gasp of fight stars (generating planetary nebulas), stellar winds and supernova explosions. 

Mochkovitch R. (1994) An introduction to the physics of type II supernova explosions , in Matter under Extreme Conditions (Springer-Verlag, Berhn). 

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