[HN Gopher] Slow-spinning radio neutron star breaks all the rules
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Slow-spinning radio neutron star breaks all the rules
Author : doener
Score : 13 points
Date : 2024-06-07 21:46 UTC (1 hours ago)
(HTM) web link (www.sydney.edu.au)
(TXT) w3m dump (www.sydney.edu.au)
| kstrauser wrote:
| I'm a layman here. This is a genuine question because I don't
| know as much about this as I'd like:
|
| Why do we expect neutron stars to spin rapidly? I understand the
| "ice skater pulling their arms in" analogy, but why should the
| pre-collapse star have been appreciably spinning in the first
| place? To my lay lack-of-understanding, if the neutron star is
| spinning slowly, then that just implies the earlier version
| didn't have a whole lot of angular momentum in the first place.
| What's wrong with that?
| Waterluvian wrote:
| Not an expert. How slow would it have to spin for it to be
| appreciably "slow" after it speeds up as a neutron star, and
| how many celestial bodies are spinning that slowly in general?
|
| So, why do bodies accrete in a non-uniform way as to inherit a
| significant spin far more often than not? Is that bias found in
| the matter being accreted? Similar to why things seem to rotate
| the same way: one direction eventually prevails?
| pfdietz wrote:
| The pre-collapse star is spinning for the same reason: any
| nonzero angular momentum in the very extended gas/dust cloud
| from which it formed gets concentrated as it collapses into the
| star. In fact, there's typically so much angular momentum it
| can't go into the star, but instead either goes into more than
| one star, or into a pre-planetary disk around the star.
| jdiff wrote:
| The skater is a small human sized object. They pull their arms
| in, don't honestly shrink much, but they still spin appreciably
| faster. When you go from something the size of a pre-collapse
| star and compare it to the size of a neutron star, the speed up
| factor is way higher. It doesn't matter how slowly you're
| spinning when big, you will be spinning fast when you get small
| as all that angular momentum must be conserved.
| sandworm101 wrote:
| Everything in space is spinning. Put three or more objects in
| space, let them fall towards each other under gravity, and the
| result will be some amount of rotation. So every star forms
| from spinning material.
| xqcgrek2 wrote:
| From all I've read for this, it should not be possible for such a
| slow star to emit anything, ie against known physics of natural
| objects.
|
| Why are they so quick to discard a technological origin?
| ceejayoz wrote:
| Because we've run into plenty of "huh we didn't think those
| existed" in astronomy so far. We'll try to understand more
| mundane possibilities first.
| ben_w wrote:
| > Why are they so quick to discard a technological origin?
|
| A sufficiently advanced society could cause any possible
| phenomena we ever observe, Occam's razor says you should look
| for other solutions first.
| goatlover wrote:
| Because as of yet, there's no evidence of ETs, but there's
| plenty of evidence for natural phenomena that were puzzling for
| a while.
| dave4420 wrote:
| My first thought was that maybe it's falling into a black hole
| and thus heavily time dilated, but the article doesn't mention
| that as a possibility.
|
| So... why isn't this a serious possibility?
| pavel_lishin wrote:
| I'm going to take a guess not backed up by any mathematics - to
| be that close to a black hole, it would have to be well within
| the Roche limit and get torn apart.
|
| Plus, I'd wager they'd be able to tell if it was eclipsed by
| the black hole at all.
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