Slashdot Mirror
Bizarre Star Could Host a Neutron Star In Its Core
ananyo writes "Astronomers say that they have discovered the first example of a long-sought cosmic oddity: a bloated, dying star with a surprise in its core — an ultradense neutron star. Such entities, known as Thorne-Zytkow objects, are theoretically possible but would alter scientists' understanding of how stars can be powered. Since Thorne-Zytkow objects were first proposed in 1975, researchers have occasionally offered up candidates, but none have been confirmed."
A star IN a star? Now I can't make fun of Sunshine anymore.
"Love heals scars love left." -- Henry Rollins
So I put a star in yo star so you can collapse into a black hole if your combined solar mass exceeds the Oppenheimer-Volkoff limit.
I heard... you know what? It's too easy.
Work sucked, until it became unemployment, when it became slightly more tolerable. -Tet
Such entities, known as Thorne-Zytkow objects, are theoretically possible but would alter scientists' understanding of how stars can be powered.
How apt this phrase is now: There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
A feeling of having made the same mistake before: Deja Foobar
"Stars with degenerate neutron cores", Astrophysical Journal, 1977.
Courtesy of the SAO/NASA Astrophysics Data System, an open-access digital library that other fields could do well to emulate...
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
I read TFA and I don't see where this comes from: but would alter scientists' understanding of how stars can be powered
It sounds like Thorne and Zytkow proposed the scenario and predicted what one would observe, followed up by people like the guy quoted in the brief article (Podsiadlowski), and these astronomers are putting forth a candidate based upon their observations being similar to what the theory suggests. I'm missing the part that alters the understanding. Podsiadlowski, by the way, has been thinking about these objects for a very long time.
While I've not heard of a Thorne-Zytkow object before, I can apply my general astronomical knowledge to explain a bit further.
The idea of an internally inert condensed object at the centre of a star is very standard: red giants have a white dwarf at their core, indeed this is how white dwarfs are formed. The weirdness is in having a neutron star instead of a white dwarf core.
The condensed object is supported by degeneracy pressure (electron degeneracy pressure for a white dwarf, neutron degeneracy pressure for a neutron star.) (Degeneracy pressure is a quantum mechanical effect. It is only appreciable at very high densities, and is not dependent on temperature.) The surface of the condensed object will be very hot, because nuclear burning is going on nearby and it is insulated from the coldness of space by the envelope of the star (i.e. the bits of star which are not the condensed object.) The density of gas just above the surface of the core will also be large, due to the high surface gravity plus the pressure of the weight of the envelope.
High temperature and high density leads to nuclear burning (combining light nuclei into heavier ones, releasing energy.) The nuclear reactions are generally very strongly dependent on temperature (e.g. one important reaction has a rate approximately proportional to temperature to the 17th power) so the burning happens in a thin layer. The 'burnt' material settles on the core, slowly enlarging it.
The gravitational attraction of the core pulling the envelope inward is largely balanced by gas pressure and radiation pressure. While stars like our sun are dominated by gas pressure, in this case radiation pressure will dominate. As the radiation escapes outward, mass is able to migrate inwards, to the thin burning layer. An equilibrium is reached between the burning/energy production rate and the mass inflow rate.
Because they are dominated by radiation pressure, it doesn't take much extra push for something at the surface of a red giant star to escape, so these stars have strong stellar winds and high mass loss rate to winds. So the envelope gets eaten from the bottom by burning and deposition onto the growing white dwarf, and from the top by mass loss. Eventually there is no envelope left and a bare white dwarf is exposed. (The final transition is quite spectacular and is called a planetary nebula.)
Heat transport in red giants is dominated by convection rather than radiation. (I think this is a general property of being dominated by radiation pressure, but I may be mistaken.) This allows material which has been close to the burning zone to mix through the star. Various secondary nuclear reactions occur there (e.g. s-process nucleosynthesis), so the products of this are mixed to the surface, where they can be observed in the spectrum. (I'm not sure whether partly-burnt material from the main burning shell can get mixed out or not.)
Evidently (according to the article) in Thorne-Zytkow objects these reactions are different from in a normal red giant and so mix different products to the surface. The star of the article has a spectrum rich in predicted reaction products of a Thorne-Zytkow object.
While white dwarf naturally grow inside stars, the process that generates neutron stars (supernovae) removes the stellar envelope, so finding a neutron star inside an envelope requires some rare post-supernova event to supply the neutron star with stellar-mass quantities of fresh gas.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
Who else was thinking "nougat"?
Who could this be? Let's see, something about defecation - Oh yes! Hello again, Shithouse Astronomer!
Another nail in the coffin of so-called "knowledge". How can you trust a belief system that CHANGES all the time?
So let's say you have a neutron star.
How does it decay? Blackholes have hawking radiation, neutron stars don't need to decay that way of course but they must eventually decay
If a neutron star emits enough energy to pass below the limit that keeps the pressure as neutrons --- and neutrons have a half-life of 14 minutes outside an atom --- do the neutrons decay into a proton (hydrogen) and an electron and become hydrogen and then start fusing again into helium?
Priest: "Universe from nothing, no laws of physics, sped up time"+ huge discrepancies. Creationism? No. Big Bang Theory
Not conclusive evidence for a Thorn-Zytkow object. FTFA:
"The star is enriched in lithium, rubidium and molybdenum. Elevated amounts of these elements are thought to arise as by-products of Thorne-Zytkow objects, which have to burn through unusual nuclear fusion pathways."
"The object is an excellent candidate, although it is perhaps not an open-and-shut case,” says Podsiadlowski. There is not quite as much of the three enriched elements as expected, he says."
Protons are stable to a period greater than 2.1 * 10^29 years (also listed as 10^36 years in the article). Free protons will/might fall apart after that time.
Free neutrons have a very short period of stability (about 15 minutes). Within dense confinement, one would wager them to be on the order of proton decay.
What you are proposing would be healthy for the physics community, so it will never happen. It is imperative that physics appear to be all knowing, especially when you talk about worm holes and the Big Bang and what will happen in 10^^100 years. We know exactly what is going on, right up until everything changes as one flawed theory is replaced by another with new flaws.
I think the other two replies are reacting to the notion that physics doesn't need to be taught, but rather just let everyone "have a go". Personally I don't think that is what you meant.
I find physics at once childish and elitist, and wish it was more humble. For example, with regard to the ether. We thought it was there, then we "proved" it was not...but today it is generally held that there is "vacuum energy" (and/or dark energy). Clearly there is an ether, and it is "made of" energy, not matter. And it is at an energy level vastly higher than 2.7K, so we need to create theories that are comfortable with this. I've done my part.
I come here for the love
My questions about the sources of your blanket statements was to point out that YOU were not backing up YOUR statements.
Einstein never made any mistakes with his theories?
String Theory doesn't change its tune every month?
There is nothing wrong with changing a theory that doesn't work. In fact, that is my position -- physics today is in the doldrums because the major theories have major problems. Those trying to provide something better/different need to be heard if we are ever going to make further progress in physics.
Talk of solids and fluids reflects the lack of scientific knowledge that was present a hundred years ago. There is no child today that would propose that. But there are plenty of scientists that have maintained that there must be an ether. In other words, there seems to be something about an ether that could explain stuff, at least in the minds of Newton, Poincare, De Pretto and Samuel Tolver Preston. Personally, I think they were on to something.
My theory says the ether is ultra high energy (which is what physicists calculate space should be composed off anyway...they just haven't managed to detect it yet), and "mechanically" as you keep saying, my "particles" are 20 orders of magnitude smaller than those of the atomic scale. Solids and fluids are at one end of a very very long scale, and my "springs" are precisely at the opposite end.
Off the top of your head, what test would you use to detect something 20 orders of magnitude smaller than a proton, and having an energy sixty to one hundred orders of magnitude higher than the background energy of space that we presently measure?
I am all for eliminating what can not be. That is how science makes progress. I just think that the last thing we have eliminated is the ether itself. We need to do more eliminating, if we can, but we also need to compose theories and models where an ether is part of the model...and see if such models can produce the results we see in the world.
Sometimes we need to carry models along for quite some time, in tandem with conflicting models. For example, the static versus expanding universe. Einstein thought it was static. We didn't kick him to the curb for this. Looking back, it didn't really matter whether we thought it was expanding or not. What mattered was that we found a way to prove it was expanding, and we have gone with that. In the future it may yet prove to not be expanding, or be expanding faster than we thought, or, or, or.
It doesn't pay to be too smug about a physics theory.
The position of the majority of the physics community on the ether has determined our direction since the time it was ruled out. And right now we have ended up with
I come here for the love