Most massive pulsar measured so far

[Martin]

http://arxiv.org/abs/astro-ph/0508050

A 2.1 Solar Mass Pulsar Measured by Relativistic Orbital Decay

 

David J. Nice, Eric M. Splaver (Princeton), Ingrid H. Stairs (UBC), Oliver Loehmer, Axel Jessner (MPIfR), Michael Kramer (Jodrell Bank), James M. Cordes (Cornell)

9 pages, Submitted to the Astrophysical Journal

 

"PSR J0751+1807 is a millisecond pulsar in a circular 6 hr binary system with a helium white dwarf secondary. Through high precision pulse timing measurements with the Arecibo and Effelsberg radio telescopes, we have detected the decay of its orbit due to emission of gravitational radiation. This is the first detection of the relativistic orbital decay of a low-mass, circular binary pulsar system. The measured rate of change in orbital period, corrected for acceleration biases, is dP/dt=(-6.4+-0.9)x10^-14. Interpreted in the context of general relativity, and combined with measurement of Shapiro delay, it implies a pulsar mass of 2.1+-0.2 solar masses, the most massive pulsar measured..."

 

The implied existence of a (pulsar) neutron start this massive has far-reaching consequences. I will list some references.

 

The six-hour period of the two-star system is gradually getting shorter as the two stars spiral in closer to each other----orbiting faster in a tighter orbit.

 

They spiral in gradually because they radiate off energy in the form of gravitational waves----mass moving back and forth, or around, radiates gravity waves analogously to how charge moving back and forth in an antenna radiates electromagnetic waves. This loss of energy, carried away by gravity waves, is what was being measured, as manifested by the speeding up of the orbit.

 

It is thought that the core of a neutron star this massive could not be made of neutrons because neutron matter is not believed to be strong enough to sustain the enormous pressure and density----the star would have long since collapsed to form a black hole. The observation of such massive neutron stars raises questions about the equation of state of the presumed quark matter, or other exotic matter, existing at the core.

 

This observation, if confirmed, would seem to disprove Smolin's CNS-multiverse conjecture, on the basis of which one would expect that any neutron star more massive than about 1.5 or 1.6 solar would collapse forming a black hole. Thus CNS predicts that a 2.1 solar mass pulsar like this should not exist, and appears to be refuted.

[Martin]

http://www.arxiv.org/abs/astro-ph/0405262

The Physics of Neutron Stars

J.M. Lattimer, M. Prakash

22 pages, 4 figures and 1 table

Science Vol. 304 2004 (536-542)

 

I think this is a good collection of facts about neutron stars. It is recent (2004) and it was published in the journal Science.

 

If someone here knows of a good online source about neutron stars and the exotic high-density matter their cores are made of, please post it. I for one, and maybe others too, would appreciate having more links.

 

Anyway, Lattimer and Prakash has a trove of info about neutron stars and I don't know anything that is more mainstream/authoritative/reliable about the subject.

 

They also have an earlier paper

http://www.arxiv.org/abs/astro-ph/0002232

which explores some of the possibilities for the kinds of matter that might be at the core of neutron stars----"quark matter", "kaon matter".

I couldnt get much out of this one, but maybe someone else can.

[Thomas Kirby]

I couldn't find where anyone made a clear estimate on when neutrons would collapse and allow a singularity to form. Neutron stars are getting pretty close to a density at which, even if the star did not collapse further, it would still be a black hole because its Schwarzschild radius would be larger than the star's radius.

 

One thing that bothers me in a lot of these articles is that they do not distinguish between a black hole and a singularity. When talking about compact masses, a singularity means zero volume. One dimension is zero whether you are talking about a point, a hoop shape (toroid, Kerr type), or any other shape, as long as the volume of the actual figure is zero or infinitely small. A black hole forms when there is a given amount of mass within a certain finite volume.

[Martin]

... Neutron stars are getting pretty close to a density at which' date=' even if the star did not collapse further, it would still be a black hole because its Schwarzschild radius would be larger than the star's radius.

 

...[/quote']

 

that is correct

 

I don't know any astrophysicist who assumes that the core of a neutron star is neutron matter. do you?

 

it might be interesting if you would find a recent article about the hypothesized internal structure of neutron stars, thomas, and post a link.

 

the astrophysicists who do this use whatever is known that is relevant from particle physics to deduce what kinds of exotic matter would be at the heart of neutron stars-----and they have various "onion" models that i have seen.

 

since you are interested, how about trying google for us and seeing if you can find some recent technical articles about the structure of n. stars

and the equation of state of the very compact stuff inside

[Thomas Kirby]

Until this week I hadn't heard of any state of matter between neutron stars and singularities in density, except maybe Einstein-Bose condensates. Many of the articles and books simply don't mention any such thing.

[insane_alien]

what about the quark stars sometimes called "strange" stars. try googling them.

[Daecon]

So instead of it being a giant nucleus, it's a giant neutron?

 

Why strange quarks? What are they usually associated with, if a neutron is just up/down quarks, where do the strange quarks come from?

[Martin]

Until this week I hadn't heard of any state of matter between neutron stars and singularities in density, except maybe[/i'] Einstein-Bose condensates. Many of the articles and books simply don't mention any such thing.

 

Thomas, this is actually a pretty exciting bunch of questions---the states of matter inside a neutron star. And since I am not expert in this I should say clearly at outset that YOUR FIRST IMPRESSION COULD BE RIGHT AND MINE WRONG.

 

in fact it could turn out that expert opinion (as presented in an authoritative source like Lattimer and Prakash) says that these objects are simply neutrons all the way down.

 

Why don't we simply paste in what they say and LOOK at it?

 

By the way even the picture that we get from worldclass mainstream experts on neutronstar physics has to be qualified by noting that nobody really knows what is inside one. what we are learning here is WHAT CAN BE INFERRED OR DEDUCED FROM PRESENTDAY NUCLEAR PHYSICS AND PARTICLE PHYSICS.

 

so Lattimer and Prakash have gathered together all the relevant knowledge gained from studying atomic nuclei and smaller stuff in the laboratory and with accelerators and using that knowledge (which is still imperfect and incomplete, like all knowledge) they have INFERRED what kinds of stuff must be inside there, at various levels where there are various different temperature, pressure and density conditions.

 

I think of it as a way of trying out the laboratory knowledge by seeing what conclusions it leads to. Does it predict that neutron stars can be only soandso massive before collapsing to hole? And if so, then what happens if you discover one that is more massive than that? So this kind of thing TESTS the current state of knowledge about matter, by astronomical observation.

 

Anyway, why don't we just paste in some part of Lattimer and Prakash and look at it?

[Martin]

BTW did you look at Figure 3 on page 21?

It is an onion diagram. In a sense disappointing to us inquisitive non-experts because they say they DONT KNOW the state of matter in the inner core. They have some ideas, but they are clearer about the outer core and the other layers. In terms of the states of matter they identify 5 different layers.

 

Figure 3 is also helpful because on the side they have some schematic pictures of the different states of matter they talk about on page 6.

 

So here's a quote from Lattimer and Prakash

http://www.arxiv.org/abs/astro-ph/0405262

 

 

----from page 6 of The Physics of Neutron Stars----

Internal Structure and Composition

 

A neutron star has five major regions, the inner and outer cores, the crust, the envelope and the atmosphere (Fig. 3). The atmosphere and envelope contain a negligible amount of mass, but the atmosphere plays an important role in shaping the emergent photon spectrum, and the envelope crucially influences the transport and release of thermal energy from the star’s surface. The crust, extending about 1 to 2 km below the surface, primarily contains nuclei. The dominant nuclei in the crust vary with density, and range from ⁵⁶Fe for matter with densities less than about 10⁶ g cm^-1 to nuclei with A approx. 200 but x approx. (0.1 to 0.2) near the core-crust interface at n approx. n₀ /3. Such extremely neutron-rich nuclei are not observed in the laboratory, but rare-isotope accelerators [31] hope to create some of them.

 

Within the crust, at densities above the neutron drip density 4 × 10¹¹ g cm^-1 where the neutron chemical potential (the energy required to remove a neutron from the filled sea of degenerate fermions) is zero, neutrons leak out of nuclei. At the highest densities in the crust, more of the matter resides in the neutron fluid than in nuclei. At the core-crust interface, nuclei are so closely packed that they are almost touching. At somewhat lower densities, the nuclear lattice can turn inside-out and form a lattice of voids, which is eventually squeezed out at densities near n₀ [32]. If so, beginning at about 0.1 n₀, there could be a continuous change of the dimensionality of matter from three-dimensional (3-D) nuclei (meatballs), to 2-D cylindrical nuclei (spaghetti), to 1-D slabs of nuclei interlaid with planar voids (lasagna), to 2-D cylindrical voids (ziti), to 3-D voids (ravioli, or Swiss cheese in Fig. 3) before an eventual transition to uniform nucleonic matter (sauce). This series of transitions is known as the nuclear pasta.

 

For temperatures less than approx. 0.1 MeV, the neutron fluid in the crust probably forms a ¹S₀ superfluid [1]. Such a superfluid would alter the specific heat and the neutrino emissivities of the crust, thereby affecting how neutron stars cool. The superfluid would also form a reservoir of angular momentum that, being loosely coupled to the crust, could cause pulsar glitch phenomena [33].

 

The core constitutes up to 99% of the mass of the star (Fig. 3). The outer core consists of a soup of nucleons, electrons and muons. The neutrons could form a ³P₂ superfluid and the protons a ¹S₀ superconductor within the outer core. In the inner core exotic particles such as strangeness-bearing hyperons and/or Bose condensates (pions or kaons) may become abundant. It is possible that a transition to a mixed phase of hadronic and deconfined quark matter develops [34], even if strange quark matter is not the ultimate ground state of matter. Delineating the phase structure of dense cold quark matter [35] has yielded novel states of matter including color-superconducting phases with [36] and without condensed mesons [35].

 

----end quote----

 

EDITED IN LATER TO RESPOND TO THOMAS KIRBY

 

Thomas, thanks much for this excellent link to "Ask the Astronomer"! It is only by accumulating links and information to compare and evaluate that we can make headway!

 

I will reply here to your post, which follows, to save having to make an extra post.

 

Your link is so interesting that I will quote a portion:

-----quote from Ask Astromer, Kirby link-----

....The cinder is prevented from further gravitational collapse because neutrons are particles with 1/2-unit of quantum spin, and only two of these can exist in the same quantum state. This produces what is called Fermi Degeneracy Pressure which at these densities and neutron star masses, can be as strong as gravity, but a repulsive force.

 

Neutrons are composed of three quarks, which are also capable of generating the same kind of degeneracy pressure, but first you have to compress the neutron star to densities of 10^16 grams/cc or higher. This requires an amount of mass in the neutron star that puts it nearly at the black hole limit for its size...about 25 kilometers in radius or less. At these densities, the neutrons in the core of this object begin to dissolve into their constituent quarks, and so in the deep interior of the cinder you end up with a 'gas' of quarks. As you continue to crank up the density even higher, the quark-state encompasses more and more of the neutron star. The problem is that such 'quark stars' are nearly the same size as the black hole limit for the amount of mass and size, so when you factor-in the relativistic effects, quark stars are probably a very unstable and fleeting phase in the life of a very massive neutron star.

---end quote---

 

However thomas I disagree somewhat with your post which follows. I believe that if a nonrotating non-electrically-charged spherical starsize mass is compressed down to where its radius is less than Schwarzschild then it MUST COLLAPSE. I see no alternative.

 

As you know, but merely for explicitness, the condition is

[math]R < \frac{2GM}{c^2}[/math]

[Thomas Kirby]

I'm not sure what everyone is thinking or assuming when they read or write terms like "black hole limit." If the term means that the star collapses further, that is very different from it simply becoming a black hole because it has enough mass within a certain volume. The latter does not mean that the former has happened. Anyone who writes about a "collapse into a black hole" is writing with precision that is not up to the standards of a scientific paper. What we need to know in these cases is when it is theorized that a neutron star undergoes further collapse.

 

This Ask the Astronomer segment gets that critically wrong. The mass is not necessarily unstable because its radius goes below its Schwarzschild radius. There isn't anything about that that requires it to collapse. If you are working out the progressive changes in the state of matter, you can't just throw up your hands when you reach the Schwarzschild radius and say that it all collapses. You need to work it out. Never mind the Schwarzschild radius, just work out the pressures and the properties of the matter involved.

[GUNITTHEORY]

G-Unit Theory dictates by definition that multiple universes do not exist. According to the standard model, it would break the first law of thermodynamics to have multiple universes as the total energy of the universe would not be constant.

If there were any connection between this universe and another, then again there would be only one universe. If there were only an intermittent connection between this universe and another, then the total energy of this universe would vary, and this would violate the first law of thermodynamics stated, "That the total energy of the universe is constant." There has never been an exception to this law, therefor there are no mutiple universes and Smolin's conjecture is false.

[Thomas Kirby]

As I remember, the laws of thermodynamics were not handed down to us by God or anyone with a status even close to that of God. How do we know that even one statement of the laws of thermodynamics is true? These are unproven assertions. The person who says that they are unproven doesn't have to prove anything. The person who says that these laws are universal and absolute has a lot to prove.

[CPL.Luke]

but they already proved themselves kirby, I'm sure if you bothered to go back and search for the proofs of these laws you would find them.

 

So at this point in time the person who claims that these laws are false has far more to prove.

[Thomas Kirby]

Circular reasoning always proves itself.

[GUNITTHEORY]

The first law of thermodynamics is valid or the technique of solving thermodynamic equations by setting one side of the equation to zero would not work. Since it works in all cases, the first law of thermodynamics is certainly valid and quite inviolate. Smolin's conjecture is quite wrong in its assertion that multiple universes exist no matter how popular it is with the scientific community at large.

Further, the first law of thermodynamics may be one of the closest algebraic forms to describe the universe which certainly borders upon the divine.

[Thomas Kirby]

The first law of thermodynamics is valid or the technique of solving thermodynamic equations by setting one side of the equation to zero would not work. Since it works in all cases' date=' the first law of thermodynamics is certainly valid and quite inviolate. Smolin's conjecture is quite wrong in its assertion that multiple universes exist no matter how popular it is with the scientific community at large.

Further, the first law of thermodynamics may be one of the closest algebraic forms to describe the universe which certainly borders upon the divine.[/quote']

 

You believe the first sentence why? The process of solving many algebraic equations involves setting one side to zero. This doesn't prove anything about the melting point of lead, the migration patterns of geese, or about the laws of thermodynamics. You and I have no way to test "all cases." Any case in which you solve the problem by assuming the first law to be true is not a test.

 

The first law of thermodynamics, "You can't win" assumes facts about the universe that we can't prove to be true. They can only be proven false.

[GUNITTHEORY]

The only reason that it is valid to set one side of a thermodynamics equation to zero is because dE=0, or the total energy of the universe is constant! References to other types of equations which use such technique are mere attempts to skirt this issue. However, I believe that other uses of this technique also rely on the concept of equilibrium in a physical system - the technique works for physical, closed systems in equilibrium. It further proves the point that Smolin's conjecture is false for this universe must be a closed system in equilibrium and not some imaginary multiple universe fancy for dE=0.

 

As far as science only being able to prove something false. I agree with you here. I find without a shadow of a doubt that Smolin's conjecture violates the first law of thermodynamics and is therefor proven false because of that fact.

[Thomas Kirby]

Have you taken vector algebra, at least the basics? If so, do you believe that it applies to reality?

 

The sum of the energy in some theoretical constructs of the universe is constant because the vector sum of all energies formed in the universe is zero. When you set one side of the equation to zero, you are being very literal. We have a situation in which matter and energy can be created and destroyed without violating either the first law or the laws of conservation of matter and energy.

[GUNITTHEORY]

A vector has both magnitude and direction.

 

According to the standard model, matter and energy are neither created or destroyed but merely change forms between one another.

 

According to G-Unit Theory, the substance of the universe, its most basic building "blocks" - G-Units, spinning permeable spherical gravitational units with a diameter of a Planck length and a mass of a Planck mass and their interactions comprise the phenomena known as matter and energy. G-Unit Theory First Revised Edition should be coming out soon.

 

The 2.1 solar mass pulsar detected by the fine gentlemen who wrote this article lends further credibility and direct sample evidence to the negation of the Smolin conjecture. In order for the conjecture to be valid, this pulsar which has been detected could not exist. Since it does exist, and the theory of the conjecture violates the first law of thermodynamics, the Smolin conjecture is proven false by logical negation backed by physical evidence and data.

 

I am a great fan of Smolin and the Ashtekar group but he was obviously wrong in asserting this or any multiple universe theory. TG, Zephrym Cochran

[Thomas Kirby]

Well, I haven't read the Smolin conjecture, but using vector analysis, the law of conservation of energy and matter proves that we can get something from nothing and that it can return to nothing.

[Martin]

I think this paper by Lattimer and Prakash has been useful

http://www.arxiv.org/abs/astro-ph/0405262

The Physics of Neutron Stars

 

and I ran across another paper, by someone named F. Weber, at San Diego State, that also tries to figure out what could be deep inside neutron stars.

Just in case someone might be interested here is the link

 

http://arxiv.org/astro-ph/0407155

F. Weber

Strange Quark Matter and Compact Stars

 

I can't evaluate or compare for reliability. I think that Lattimer and Prakash is pretty clearly OK (elite mainstream citations).

But someone might want to look at F. Weber too.

 

BTW he also has an onion diagram (it kills me, all these guys guessing what is inside a neutron star! that's our species for ya.)

[GUNITTHEORY]

According to the standard model, matter and energy may neither be created nor destroyed, but may only change forms. Therefor, you may not get something from nothing within the universe, and though I am not up on vector analysis, it is mistaken in its interpretation of this particular case. I am able to tell because it is illogical. Matter and Energy being conserved, means they change forms - not coming from nothing or returning to nothing. I would try applying physical chemistry to the problem instead of vector analysis.

G-Unit Theory defines the universe as continuous on its interval. Therefor, there is no nothing within the universe. Every bit of the universe is composed of G-Units, spinning permeable spherical gravitational units with a diameter of a Planck length and a mass of a Planck mass. The resolution of the universe being on the level of a Planck length, what we observe popping mysteriously out of "nothing" is symmetrical gravitational octahedral formation. Small particles are crystallizing out of the highly geometrical spacefoam. Present science can only see, say with an electron microscope or such, *10-15 meters , possibly *10-20 meters , on a good day. The resolution of the universe is on the level of a Planck length, *10-35 meters. Everything above *10-20 meters is considered nothing according to the standard model. G-Unit Theory goes all the way down to the Planck length and can explain these phenomena that the standard model only guesses at.

TG.Zephrym Cochran, for all you star trek fans.

[Thomas Kirby]

Look up "vacuum pair formation."