4 ms·

There are several subtypes of neutron stars. My favorite is the magnear [1]. These are extremely rare and I believe don't last that long but while they do they

by jmyeet 4y ago

There are several subtypes of neutron stars. My favorite is the magnear [1]. These are extremely rare and I believe don't last that long but while they do they have an unbelievable strong magnetic field. I'm talking a quadrillion times stronger than Earth's, strong enough to literally rip atoms apart from a sizeable distance. The article mentions the equation of state. Fun fact: neutron stars are probably the most complex objects in the Universe. Black holes by comparison are quite simple: describle with three quantities (mass, spin, electric charge). An equation of state would tell us how large these can get, for example. Consider the nucleus of a normal atom. We know and have mapped out electron shell structures. Nuclei too have structure but it's way more inscrutable and complex as you have to deal with the electric repulsion between protons, the strong interaction between quarks (and gluons) and the strong interaction between nucleons. AFAIK we don't really have a good model for this. Now imagine that scaled up to something 20km across where gravity has also become a significant force and obviously we don't have a quantum model for gravity anyway. In addition to all of that you have to deal with fluid dynamics. The article mentions nuclear pasta and theorized crystalline structure within a neutron star but in outer layers its likely it acts more like a fluid. And then there's things can collide in unbelievable energetic interactions, such that we can detect the ripples in space-time billions of light years away. We're talking 5-10 Solar masses converted to energy in less than a second. [1]: https://en.wikipedia.org/wiki/Magnetar https://en.wikipedia.org/wiki/Magnetar EDIT: fixed Solar mass typo

bell-cot 4y ago
Quibbles: > Black holes by comparison are quite simple: describle with three quantities (mass, spin, electric charge). For an actual black hole (vs. theoretical-in-a-vaccuum one), I believe 2 other number are required - to specify which way the spin axis points. [EDIT - still not right. 11 numbers are needed to cover everything; see my Wikipedia cite below.] > We're talking 50-10 Solar masses converted to energy... Obvious "50-10" typo. But beyond ~6 Solar masses total, at least one of the two object will have long-ago collapsed into a black hole.
- zaarn 4y ago
  The spin axis isn't a valuable reference since it depends on your frame of reference, which is a concept that gets rather ambiguous as you get close to a black hole anyway. Plus you can just "rotate" a black hole to get it to have the same spin axis as another black hole. You can't "rotate" or "translate" a black hole in space to make the other three numbers change. Those require ingesting matter or emitting hawking radiation and that is the only thing that changes those properties.
  - bell-cot 4y ago
    I'm figuring that the low-rent planets, stars, etc. in the vague vicinity of an actual black hole would provide a fine frame of reference. > Plus you can just "rotate" a black hole to get it to have the same spin axis as... Quip: If you have the tech & budget to meaningfully rotate a spinning black hole, then you've got the tech & budget to change the other parameters, too. FWIW - Wikipedia's answer is that 11 numbers (or 2 scalars and 3 vectors) are needed to fully spec. a stable black hole - https://en.wikipedia.org/wiki/Rotating_black_hole#Types_of_black_holes https://en.wikipedia.org/wiki/Rotating_black_hole#Types_of_b...
    - zaarn 4y ago
      There is a cheap and even for current humanity achievable way to rotate a black hole; change your frame of reference. That is not only true for angular momentum but linear momentum and position. Those are entirely dependent on the observer and their frame of reference. Spin, magnetic charge and mass are not. Two black holes who differ only by their position, linear and/or angular momentum but are equal in all other parameters are not distinguishable from simply seeing the same black hole twice from a different perspective. Two black holes who differ in any of the three properties of mass, spin or magnetic charge are distinguishable by those properties (but even that is arguable to some extend). edit: The rent prices of a planet don't matter since frame of reference is an actual term here, there is no frame of reference more valid than any other for determining the linear or angular velocity or the position of a black hole.
Idiot_in_Vain 4y ago
[flagged]
- rbanffy 4y ago
  A polite way to say that would be to point out the mistakes and correct them, so we all could learn.
  - Idiot_in_Vain 4y ago
    I don't know where to start. >> Consider the nucleus of a normal atom. We know and have mapped out electron shell structures. Nuclei too have structure but it's way more inscrutable and complex as you have to deal with the electric repulsion between protons, the strong interaction between quarks (and gluons) and the strong interaction between nucleons. AFAIK we don't really have a good model for this. We have a great model for this, it's called quantum chromodynamics (QCD). >> neutron stars are probably the most complex objects in the Universe Nope, a human brain is far far far more complex than a neutron star. >> Black holes by comparison are quite simple: describle with three quantities (mass, spin, electric charge) Not exactly. Every isolated unstable black hole decays rapidly to a stable black hole; and (excepting quantum fluctuations) stable black holes can be completely described (in a Cartesian coordinate system) at any moment in time by these eleven numbers: mass–energy M M, linear momentum P (three components), angular momentum J (three components), position X (three components), electric charge Q Q. On top of that a study by Sasha Haco, Stephen Hawking, Malcolm Perry and Andrew Strominger postulates that black holes might contain "soft hair", giving the black hole more degrees of freedom than previously thought. https://en.wikipedia.org/wiki/No-hair_theorem#Soft_hair https://en.wikipedia.org/wiki/No-hair_theorem#Soft_hair
    - AnimalMuppet 4y ago
      Quantum chromodynamics may be a "great" model, but it's horrible to try to actually calculate with on the scale of a neutron star.
- wholinator2 4y ago

by jmyeet 4y ago

bell-cot 4y ago

Quibbles: > Black holes by comparison are quite simple: describle with three quantities (mass, spin, electric charge). For an actual black hole (vs. theoretical-in-a-vaccuum one), I believe 2 other number are required - to specify which way the spin axis points. [EDIT - still not right. 11 numbers are needed to cover everything; see my Wikipedia cite below.] > We're talking 50-10 Solar masses converted to energy... Obvious "50-10" typo. But beyond ~6 Solar masses total, at least one of the two object will have long-ago collapsed into a black hole.

zaarn 4y ago
The spin axis isn't a valuable reference since it depends on your frame of reference, which is a concept that gets rather ambiguous as you get close to a black hole anyway. Plus you can just "rotate" a black hole to get it to have the same spin axis as another black hole. You can't "rotate" or "translate" a black hole in space to make the other three numbers change. Those require ingesting matter or emitting hawking radiation and that is the only thing that changes those properties.
- bell-cot 4y ago
  I'm figuring that the low-rent planets, stars, etc. in the vague vicinity of an actual black hole would provide a fine frame of reference. > Plus you can just "rotate" a black hole to get it to have the same spin axis as... Quip: If you have the tech & budget to meaningfully rotate a spinning black hole, then you've got the tech & budget to change the other parameters, too. FWIW - Wikipedia's answer is that 11 numbers (or 2 scalars and 3 vectors) are needed to fully spec. a stable black hole - https://en.wikipedia.org/wiki/Rotating_black_hole#Types_of_black_holes https://en.wikipedia.org/wiki/Rotating_black_hole#Types_of_b...
  - zaarn 4y ago
    There is a cheap and even for current humanity achievable way to rotate a black hole; change your frame of reference. That is not only true for angular momentum but linear momentum and position. Those are entirely dependent on the observer and their frame of reference. Spin, magnetic charge and mass are not. Two black holes who differ only by their position, linear and/or angular momentum but are equal in all other parameters are not distinguishable from simply seeing the same black hole twice from a different perspective. Two black holes who differ in any of the three properties of mass, spin or magnetic charge are distinguishable by those properties (but even that is arguable to some extend). edit: The rent prices of a planet don't matter since frame of reference is an actual term here, there is no frame of reference more valid than any other for determining the linear or angular velocity or the position of a black hole.

Idiot_in_Vain 4y ago

[flagged]

rbanffy 4y ago
A polite way to say that would be to point out the mistakes and correct them, so we all could learn.
- Idiot_in_Vain 4y ago
  I don't know where to start. >> Consider the nucleus of a normal atom. We know and have mapped out electron shell structures. Nuclei too have structure but it's way more inscrutable and complex as you have to deal with the electric repulsion between protons, the strong interaction between quarks (and gluons) and the strong interaction between nucleons. AFAIK we don't really have a good model for this. We have a great model for this, it's called quantum chromodynamics (QCD). >> neutron stars are probably the most complex objects in the Universe Nope, a human brain is far far far more complex than a neutron star. >> Black holes by comparison are quite simple: describle with three quantities (mass, spin, electric charge) Not exactly. Every isolated unstable black hole decays rapidly to a stable black hole; and (excepting quantum fluctuations) stable black holes can be completely described (in a Cartesian coordinate system) at any moment in time by these eleven numbers: mass–energy M M, linear momentum P (three components), angular momentum J (three components), position X (three components), electric charge Q Q. On top of that a study by Sasha Haco, Stephen Hawking, Malcolm Perry and Andrew Strominger postulates that black holes might contain "soft hair", giving the black hole more degrees of freedom than previously thought. https://en.wikipedia.org/wiki/No-hair_theorem#Soft_hair https://en.wikipedia.org/wiki/No-hair_theorem#Soft_hair
  - AnimalMuppet 4y ago
    Quantum chromodynamics may be a "great" model, but it's horrible to try to actually calculate with on the scale of a neutron star.
wholinator2 4y ago