Posted on 08/11/2011 2:05:14 PM PDT by LibWhacker
Intense pressure can force neutrons into cubes rather than spheres, say physicists
Inside atomic nuclei, protons and neutrons fill space with a packing density of 0.74, meaning that only 26 percent of the volume of the nucleus in is empty.
That's pretty efficient packing. Neutrons achieve a similar density inside neutron stars, where the force holding neutrons together is the only thing that prevents gravity from crushing the star into a black hole.
Today, Felipe Llanes-Estrada at the Technical University of Munich in Germany and Gaspar Moreno Navarro at Complutense University in Madrid, Spain, say neutrons can do even better.
These guys have calculated that under intense pressure, neutrons can switch from a spherical symmetry to a cubic one. And when that happens, neutrons pack like cubes into crystals with a packing density that approaches 100%.
Anyone wondering where such a form of matter might exist would naturally think if the centre of neutron stars. But there's a problem.
On the one hand, most neutron stars have a mass about 1.4 times that of the Sun, which is too small to generate the required pressures for cubic neutrons. On the other, stars much bigger than two solar masses collapse to form black holes.
That doesn't leave much of a mass range in which cubic neutrons can form.
As luck would have it, however, last year astronomers discovered in the constellation of Scorpius the most massive neutron star ever seen. This object, called PSR J1614-2230, has a mass 1.97 times that of the Sun.
That's about as large as theory allows (in fact its mere existence rules out various theories about the behaviour of mass at high densities). But PSR J1614-2230 is massive enough to allow the existence of cubic neutrons.
Astrophysicists will be rubbing their hands at the prospect. The change from spherical to cubic neutrons should have a big influence on the behaviour a neutron star. It would change the star's density, it's stiffness and its rate of rotation, among other things.
So astronomers will be getting their lens cloths out and polishing furiously in the hope of observing this entirely new form of matter in the distant reaches of the galaxy.
I am reassured by the gnat-gnat thing. You don't suppose there's a combined solar mass in the asteroid belt, do you?
And, say, while we're on the subject:
If, as an object falls into a black hole, some of its energy is radiated outward at the event horizon and escapes the black hole, why isn't ALL of its energy radiated outward to escape the black hole?
Current thinking seems to be that some of the object's energy is radiated outward at the event horizon but that most of the object passes through the event horizon to be crushed into who-know-what by the intense gravity of the black hole. There's fantastic speculation about what happens then. Some suggest that it enters some new dimension or parallel universe or somesuch. According to theory, its energy/mass can never escape the black hole.
Why is it necessary to speculate about all this?
Why could it not be that the gravity of the black hole--at the event horizon--is sufficient to convert all of the object's matter into energy that is irradiated outward?
I suppose I know the answer: The variation in size of black holes indicates that some contain more matter/energy than others, and if it were as I suggested above, then all black holes would be the same size.
So, if that be so, then it seems to me that anything falling into a black hole (past the event horizon) must be converted into energy and that that energy is compressed constantly into something whose nature can be known only mathematically. Is there a tipping point at which enough of this something explodes into a Big Bang? Maybe it takes a quantity of energy equal to that of the entire universe for this to happen?
If this be the case, then there is a sufficient quantity of energy that, when combined and compressed beyond a tipping point, CAN escape the gravity of a black hole.
I know you can explain this, Joe. Thanks. ~S
Wikipedia has a pretty interesting article on supernovae, SB. Check out the "Current Models" section.
JB's correct about the likelihood of a collision. The analogy I've heard, iirc, goes something like this: Suppose the continental United States were as flat as a pool table and three basketballs were set to rolling around at random on it, none of them within a thousand miles or so of its nearest neighbor, and each moving in a random straight line direction with a speed of a couple of miles per year. When a basketball encounters a coastline or the Canadian or Mexican border, it bounces back toward the interior of the country. (1) How long would you have to wait, on average, before two of them collided? (2) Call one of them the Sun. How long would you have to wait (i.e., what's the expected value?) before it collided with one of the other basketballs? Longer than the age of the universe.
Everyone seems to be holding their breath waiting for more data. For example, nobody has any idea what percentage of stars are brown or red dwarfs yet. Also, the mass distribution of the stars we can see best (our neighbors in the Orion arm of the Milky Way) is known not to be representative of stars in the Milky Way as a whole; the center of the Milky Way has a different distribution, as does the halo, etc.
Taking this into account, and assuming that the nearest neighborhood is most representative with regard to the red dwarfs, the % distribution of the local galactic stellar population is as follows, taking all main sequence (V), subgiants (IV) and subdwarfs (VI) together (by far most of these are V anyway), but giants (III) separate: O and B: 0 A: 1 % F: 3 % G: 6 % K: 14 % M: 70 % White dwarfs: 5 % Giants (III): 1 % (The % of M may actually be 72% and of F and K 1 % lower each). Mass distribution is indicated here: http://www.chara.gsu.edu/~thenry/RECONS/mf.2009.0.html
Thanks, Lib. I feel much better. I coming out from under the bed.
First, let me state for the record that I'm not an astrophysicist, nor do I even play one on TV. $:-)
That said, to answer your first question, no, the asteroid belt has nothing near stellar mass. In fact it, along with every other bit of matter in Sol's neighborhood, including all planets plus everything in the Kuiper Belt and the Oort Cloud, could easily reside within the sun's existing diameter. So nothing to worry about there.
As for black holes and the effects of their event horizons (Schwarzchild Radius), well, no one knows for sure. Physics as we understand it ends there, because once gravity has overwhelmed all the other forces in nature, theory contends that there is nothing left to prevent mass from collapsing to infinity. Nature tends to abhor infinities, though, and the fact that singularities do have mass tells us that something is still there.
As I understand it, when matter hits the event horizon it is compressed instantly (to our time scale -- at the event horizon it would appear as taking forever). This terrific change in density heats the consumed matter to billions of degrees and unleashes an enormous burst of energy mostly in the X and Gamma Ray bands, so not all the matter that falls into a singularity actually makes it past the event horizon. But the vast majority does, since gravity has no negative state. Even though these bursts of energy will equal an average star's total output for a thousand years in a single second, remember that this energy is being derived (if I'm not mistaken) from total mass/energy conversion, so a little matter makes for a lot of X-Rays.
I think what you are speaking of is the phenomenon of 'Hawking Radiation', where particle-pair created at the edge of the Schwarzchild Radius are separated -- one falls in and the other flys away in the opposite direction. This effect is constant at the event horizon because black holes are so dense that the EM fields surrounding them can generate matter out of empty space. It is through this process that black holes can literally evaporate over time if not fed, something that smaller singularities are more prone to because of their higher surface-area to volume ratio.
And the fact that this too can occur does, to me anyway, remove any theories that matter entering a black hole "exits" our spacetime continuum -- it remains here, although in a state that we cannot observe and theory can only guess at.
Thanks for this explanation, Joe. It makes a lot of sense. ~S
...Fascinating, Good on yer...(-;)
Who are these morons???
Are they actually running around loose???
If there isn't a Nobel prize for that, there ought to be.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.