- #1
FayeKane
- 31
- 0
I've numbered them so you can just include it in your reply instead of screwing around with
tags.STELLAR IGNITION AND LIFE
1 -- How long it takes for a protostar to ignite, once hydrogen ignition begins? For a million-mile wide star, it can't be less than two seconds (distance to center at c), but is it on that scale, or hours, or what?
2 -- If you're outside the thing, will it take decades for the photons to work their way to the surface as happens in fully switched-on stars? Does the event look like a sudden flash, or do more and more photons leak out and it gets brighter slowly?
3 -- Probably a dumb question and I'm too lazy to renumber the rest.
4 -- Do neutron stars support fusion? If not, why can we see them? Is it just blackbody radiation? Is it synchrotron radiation from the rotating magnetic field? Is the emission spectrum of neutron stars radically different than normal stars?DEATH
5 -- Is a supernova just an ordinary-but-large nova which finally destroys the star, or is there a different mechanism going on in supernovae?
6 -- When they finally burn out and nova, I doubt that stars become completely dark all of a sudden because the photons have to find their way through all that hydrogen. So what does the light curve look like between when the star dies, and when it collapses enough to retrigger fusion? Is the temporary decline in brightness even detectable?
7 -- For a million-mile-wide star, when it finally goes out, how long does it take for the star to fall into the center before it rebounds as a nova?
8 -- What fraction of its original diameter does a star collapse to before it rebounds as a nova? Is it the same for supernovae?
9 -- Is the fractional diameter before exploding the same for a supernova, or do supernovae crush much much smaller before they're totally destroyed?
10 -- If a star cannot support fusion before going supernova, what causes the bright flash? Does fusion restart, but too late to stop the collapse?
When a supernova "goes black hole", the whole star does NOT collapse into it. That surprises me because most of the star is under huge inward pressure and there's something in the middle pulling it in even harder than the weight from above is pushing. SO:
11 -- For how many Swartzchild radii does material get sucked into the hole, as opposed to being blasted into space? How far in miles, and what fraction of the supernova is that?
12 -- Does any of the former star remain orbiting the black hole, or is it all blasted away?
13 -- What is the typical rotation rate for a black hole? It must be, uh... astronomical. Does this affect the Swartzchild radius in the same way the the Earth is oblate at the equator? What's the radius of a typical black hole, anyway?
14 -- Does stuff being pulled into the hole contribute significantly to the brightness of a supernova?
15 -- Are heavy supernovae a lot brighter than ones originating in stars which do not form black holes due to this?
16 -- Do atomic nuclei exist in a neutron star, or is it just a mass of pure neutrons? (That one may be a stupid question).
17 -- Is there a name for the process of electrons and protons being squeezed so tightly that they form neutrons?
18 -- If neutrons stars are pure neutrons, where do the photons in its blackbody radiation come from, and what does that do to the neutrons?
19 -- How much wider is a neutron star at the equator than the poles, due to rotation?
20 -- I think I remember that pulsars slow down due to the drag of their magnetic field on the interstellar medium. Is that correct, and if so, why doesn't the rotational axis eventually become the magnetic axis due to this force? Do we see this happening? Could we even see it? I guess the evidence would be a pulsar dimming, but that's surely happening anyway.ELEMENT FRACTION AND DISTRIBUTION
21 -- Do heavy elements fall to the center of stars like in planets, or is element weight irrelevant in the middle of a nuclear explosion? Does layering occur outside the fusion core?
22 -- What percent metals (i.e., > H) can a star can be and still support continuous fusion?
23 -- What percent metals finally disallows fusion restart, and a supernova occurs?
24-- What percent of a supernova remnant becomes metals? How many star populations can there be before the hydrogen density is too low to support ignition of another star? When that happens, what will condense out in stellar nurseries, huge planets?
25 -- How wide can a non-fusionable mass get from pure accretion before it collapses into a neutron star just due to gravitational pressure at the center (with no supernova)? Will that EVER happen, or does the rate of increase of the radius due to new material eventually exceed the rate at of core pressure increase, since the new stuff is so far away from the center? Will a continually-accreting neutron star ever collapse into a black hole for this reason?GALAXIES AND GALACTIC NUCLEI
Since college, I haven't kept up like I should have.
26 -- Did "active galactic nuclei" and quasars turn out to both be the same thing?
27 -- Is there any difference between galaxies with an extremely bright center object and normal galaxies? That is, is there a continuum of galactic nucleus activity, or are there discontinuous classes of galactic centers?
28 -- Why are there no nearby quasars (or are there?)
29 -- Does the black hole at the center fa a galaxy run out of stuff to fall into it and (presumably slowly) become dark?
30 -- What is the eventual fate of very old galaxies? Do they all either become torn apart by close encounters, merge, or wrap themselves into an elliptical? Do very old ellipticals become spherical and just sit there forever?
31 -- Are there any galaxies we know of which have entirely burned out, or does the material of dead stars ALWAYS form new ones?
32 -- How can the leftovers of supernovae condense into a viable star when there wasn't enough hydrogen fraction there to support fusion when it was a star the last time? Is there some process that isolates hydrogen in supernova remnants? Does free interstellar hydrogen dilute the metals in supernova remnants enough to "replenishes" the fusion capability?
33 -- Eventually, will the metals fraction in old galaxies become too high to support any stars at all, and if so, how long will that be? How many star populations? Or is there some process that breaks heavy atoms apart into hydrogen again? (probably thermodynamically impossible at a large scale)
34 -- Where does a galaxy's angular momentum come from? That is, why did the gas and dust it condensed from have an angular momentum? I would think the atoms and molecules are bouncing around randomly. Is it due to angular momentum in the quantum fluctuations during the big bang? Is there net angular momentum in a pressurized cylinder of air? Do galaxy clusters have net angular momentum, or just galaxies?TOTALLY IRRELEVANT
35 -- In Clarke's 2010, the crappy sequel to 2001, Jupiter ignited because more monoliths were placed on it until its mass was sufficient for fusion. Is that impossible since the monoliths were not made of hydrogen and would sink to the center, with the hydrogen rising to the top where it's not dense enough to ignite no matter how many monoliths you add?THANK YOU,
-- Faye Kane, padwan among Jedi
PS:
You know you're old when the "25 and 50 years ago in Sky and Telescope" column is about articles you've already read. It happened to me with the "25" ones. There ought to be a small celebration among his peers when this happens to an astronomer--although it's scary, like when you're little and you see a dead mouse in the fall and you come back in the spring and the mouse is gone
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