When a star 'explodes'

  1. When a star comes to the end of one phase in its life (eg red giant -> white dwarf), or simply 'explodes', it results in the emission of a huge amount of matter (and energy, of course).

    But what form does that matter take ??

    If the star has been cool enough (or when the emitted matter cools sufficiently), is the matter in the form of dust? Or larger chunks? And how large can these chunks be?
  2. jcsd
  3. mfb

    Staff: Mentor

    Photons, neutrinos, protons, electrons, probably some neutrons as well. They can accelerate dust somewhere else, but the process is so high-energetic that I would not expect much dust from the supernova itself.

    Edit: Oh, I forgot other nuclei, right. Apart from hydrogen, we are all made out of those nuclei!
    Last edited: Feb 19, 2013
  4. So the star will basically 'spray' elementary stuff into space. That stuff must include nuclei - maybe as ions which can later recombine with electrons, also sprayed out.

    But surely, given the right conditions, atomic matter must be a strong candidate. So the question is just how big these chunks can be. Or, alternatively, is the cloud of matter blown off as ions/atoms simply waiting for gravitational collapse (or gravitationally attracted to a larger mass) before it can gain any real solidity - almost like squeezing snow to form a snowball or (with more pressure) a block of ice?

    I appreciate that there may be some explosions (eg supernova) which will, I agree disrupt any assembly. But what about events like the Red Giant transition to White Dwarf ... how powerful and cool (thermally) are those ejections?
  5. Chronos

    Chronos 10,349
    Science Advisor
    Gold Member

    Red giant transition to white dwarf is rather quiet, although they do tend to blow off their outer layers creating planetary nebula. It is generally thought these ejecta are composed of gas and dust. It is certainly possible 'chunks' could form during this process, but, what, if any, size constraints may exist are unclear.
  6. So, does that indicate that the heavier elements which are part of accretion discs that form stars with rocky planets, come from 'Red giant transitions', or from the exploded cores of super nova?
    I didn't think that the heavy elements found in the earth could have been produced in the ejected layers of a Red giant.

  7. Chronos

    Chronos 10,349
    Science Advisor
    Gold Member

    Correct, elements heavier than iron/nickel can only be produced by supernova. But, there is an abundance of lighter elements on earth than can be produced by average stars. Earth is composed of a combination of stellar and supernova ejecta.
  8. Hello! I'm new in the forum and I was reading this post, and I also have a question about the size of the chunks.
    For example, gold is heavier than iron, so it is created during a supernova explosion (please correct me if I'm wrong). So, how big are those dust particles that end up in space? We can find gold on earth in gold mines, for example. How it comes that this gold dust comes together to form bigger chunks that can be mined?
    Thank you and sorry for my ignorance :)
  9. mfb

    Staff: Mentor

    Earth was completely molten initially (and most of it still is), the elements clumped together afterwards due to chemical reactions on earth.
  10. Thanks for your answer! As I understand, the different temperatures of the molten earth did like a separation process on the mixed dust and that's why we can find deposits?
    Could this also mean that across all the globe there is still dust of gold and uranium, for example, mixed within the rocks and sand we walk on daily?
  11. Drakkith

    Staff: Mentor

    Yes, there are trace amounts of those elements practically everywhere.
  12. mfb

    Staff: Mentor

    Sea water has ~3 micrograms of uranium per liter, and rock has about 4 micrograms of gold per kg - with local peaks of some milligrams.

    Those traces are a significant problem for neutrino experiments, for example - you always have some radioactive elements remaining in the detector.
  13. Unexpectedly, many presolar grains do come from supernovae. They namely contain calcium mostly in calcium 44.

    This could only have come from titanium 44. But the half-life of titanium 44 is mere 59 years.

    This proves that the nebula must have somehow cooled within a few decades to the point where titanium could freeze into minerals which rejected then existing calcium - but incorporated titanium 44 before it decayed into calcium.
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