So any explanation offered...
For how the star turned itself inside out and then exploded? Or is the inner material moving faster than the outer ( and so overtaken it)?
An X-ray study of Cassiopeia A, one of the youngest exploded stars in our galaxy, has found that it not only blew up, but also ripped its insides out in the process. Cas A before and after supernova Before and after the Cas A supernova. Left: NASA/CXC/M Weiss; Right: NASA/CXC/GSFC/U.Hwang & J Laming Credit: NASA Cas A, …
A star dies by imploding, once it's internal nuclear reactions can no longer make enough heat to fight gravity.
If it started as a completely symmetric sphere it would collapse to a singular point, but stars are not completely symmetric. The evidence (fron observations of Betelgeuse) is that stars about to explode get pretty warty! The implosion will therefore go faster from some directions than others, and the faster-moving bits will slam through the centre and out the other side.
Something like that, anyway. Magnetohydrodynamics with nuclear processes being driven by the moving medium depending on its temperature and pressure would make for a VERY tough modelling problem.
Supernovae are certainly where the iron in the universe comes from.
About 10% of asteroids contain sizeable amounts of iron and are classified as M-Type bodies. They show show in the early solar system, dust particles seeded with iron from supernovae accreted into planetismals some of which became large enough and hot enough, through impacts and radioactive heating to fractionate with the dense iron and nickel sinking towards the core. A few tens or hundreds of millions of years later, some of these bodies were in turn smashed up by major impacts producing asteroids and iron meteorites.
I am not totally sure that is correct: I understood it that fusion processes create all the elements up to and including iron at which point the fusion process is in fact energy neutral - no more elements are then made and the star cools down as more or less an iron sphere with not much else going on, and then the implosion adds more energy BACK into the star and it goes supernova creating all the heavier than iron elements up to and including things like lead, gold and the radioactive elements and even transuranics.
Hmm. It seems that's not quite right either and indeed no one quite knows
http://en.wikipedia.org/wiki/Supernova_nucleosynthesis
Over to a self appointed wikiexpert :-)
"I am not totally sure that is correct: I understood it that fusion processes create all the elements up to and including iron at which point the fusion process is in fact energy neutral - no more elements are then made and the star cools down as more or less an iron sphere with not much else going on..."
Well, kind of. My understanding, if I remember my physics classes from my dim and distant college past, is that there are actually several fusion processes happening in a star at once (even just hydrogen fusion can take place in one of several different ways). Iron is the bottom of the hill for most of the fusion processes, but there are also different fusion processes (which occur inside stars to varying degrees simultaneously) that produce nickel and cobalt as well. Those are also, if I recall correctly, exothermic, so you can end up with iron, nickel, and cobalt from exothermic processes but everything above that point is endothermic.
On a side note, I remember being at an orgy some years ago and geeking out about this stuff, to the point that "stellar nucleosynthesis" is still, a number of years later, the slang term for "group sex" in my social set.
Iron is the "bottom of the hill" from a fusion standpoint. For any element lighter than iron, you get energy by fusing stuff to make it.
Iron and beyond take energy to make via fusion. So as a star runs out of hydrogen, it starts fusing helium and making carbon (NOTE: this is a gross oversimplification). Then the star runs out of helium, and starts fusing carbon. Eventually, a big start has a bunch of iron. It tries to fuse that, but that doesn't make energy, and the star runs out of ooomph to keep itself from imploding. Thus - lots of iron sprayed about.
For a REALLY big star, as it implodes, it starts making antimatter (pair production catastrophe), and then it REALLY goes BOOM. Otherwise, it either makes a dwarf star, a neutron star, or a black hole, with either a fizzle, a bang, or a BANG, respectively.
"...has a mass more than three times of our Sun, containing 0.13 times more iron, 0.03 times more sulphur and 0.01 times more magnesium."
Using multipliers greater and less than 1 in the same sentence, all with the words 'more' and 'times' which implies the last three should be 113%, 103% and 101% is confusing. Is the mass >300% that of the sun, or >400%? If it's only >300%, where's the cutoff between 1+x and just x?
If I'm not mistaken, 13% of the mass of our friendly local star is nothing less than over 400 billion times the mass of our lowly planet.
And our Sun is rather smallish as far as stars are concerned.
Oh, and our galaxy alone contains 400 billion of the things.
Thank you for your time, you may now go and blow your mind mulling over all this :)
You forgot to mention that's only a sixth of the galaxy. The other five-sixths is something wierd that we're calling "dark matter" until we can work out how to get a better look at it.
And there are nearly as many galaxies in the (observable) universe as there are stars in this one.
And that lot, including the dark matter, is only about a quarter of the whole. The other three-quarters is somerthing even wierder than dark matter that we're calling "dark energy".
Now, do we have a volunteer to stick his head into the total perspective vortex?
I see this great wodge of iron, magnesium, sulphur, silicon and oxygen, condensing back upon itself to form a sphere approx 8000 miles diameter, with enough long-lived radioactives (U238, Th232, K40) in its core to keep it hot for a few gigayears afterwards - apart from a solid crust partially covered with liquid hydrogen oxide.
In fact, could such a body support life?
But how where would the kinetic energy of your imploding star go? The problem with stars that implode is that its magnificent gravity starts directing everything towards a central point. As the core density increases, the pressure increases and the star tears itself apart. Depending on its size, it either loses its outer layers (becomes a white dwarf), loses everything but its core which collapses (forms a neutron star) or it collapses fast enough that its core is pushed beyond the Chandrasekhar limit (becomes a black hole).
This isn't the whole story as there are many outcomes and types of star. Who knows what creates Preon and Quark stars?
What you're after is a brown dwarf - something larger than Jupiter but smaller than a red dwarf star, where nuclear fusion in the core generates just enough heat that the outer layers are the right temperature for liquid hydrogen oxide. Such a place might harbour life long after all normal stars have burned out and the universe has gone dark.