A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes, and some hypothetical objects (e.g. white holes, quark stars, and strange stars), neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of 10 kilometres (6.2 mi) and a mass of about 1.4 solar masses. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.
Once formed, they no longer actively generate heat, and cool over time; however, they may still evolve further through collision or accretion. Most of the basic models for these objects imply that neutron stars are composed almost entirely of neutrons (subatomic particles with no net electrical charge and with slightly larger mass than protons); the electrons and protons present in normal matter combine to produce neutrons at the conditions in a neutron star. Neutron stars are partially supported against further collapse by neutron degeneracy pressure, a phenomenon described by the Pauli exclusion principle, just as white dwarfs are supported against collapse by electron degeneracy pressure. However, neutron degeneracy pressure is not by itself sufficient to hold up an object beyond 0.7M☉ and repulsive nuclear forces play a larger role in supporting more massive neutron stars. If the remnant star has a mass exceeding the Tolman–Oppenheimer–Volkoff limit of around 2 solar masses, the combination of degeneracy pressure and nuclear forces is insufficient to support the neutron star and it continues collapsing to form a black hole. The most massive neutron star detected so far, PSR J0740+6620, is estimated to be 2.14 solar masses.
Neutron stars that can be observed are very hot and typically have a surface temperature of around 600000 K. They are so dense that a normal-sized matchbox containing neutron-star material would have a weight of approximately 3 billion tonnes, the same weight as a 0.5 cubic kilometre chunk of the Earth (a cube with edges of about 800 metres) from Earth's surface. Their magnetic fields are between 108 and 1015 (100 million to 1 quadrillion) times stronger than Earth's magnetic field. The gravitational field at the neutron star's surface is about 2×1011 (200 billion) times that of Earth's gravitational field.
As the star's core collapses, its rotation rate increases as a result of conservation of angular momentum, and newly formed neutron stars hence rotate at up to several hundred times per second. Some neutron stars emit beams of electromagnetic radiation that make them detectable as pulsars. Indeed, the discovery of pulsars by Jocelyn Bell Burnell and Antony Hewish in 1967 was the first observational suggestion that neutron stars exist. The radiation from pulsars is thought to be primarily emitted from regions near their magnetic poles. If the magnetic poles do not coincide with the rotational axis of the neutron star, the emission beam will sweep the sky, and when seen from a distance, if the observer is somewhere in the path of the beam, it will appear as pulses of radiation coming from a fixed point in space (the so-called "lighthouse effect"). The fastest-spinning neutron star known is PSR J1748-2446ad, rotating at a rate of 716 times a second or 43,000 revolutions per minute, giving a linear speed at the surface on the order of 0.24 c (i.e., nearly a quarter the speed of light).
There are thought to be around one billion neutron stars in the Milky Way, and at a minimum several hundred million, a figure obtained by estimating the number of stars that have undergone supernova explosions. However, most are old and cold and radiate very little; most neutron stars that have been detected occur only in certain situations in which they do radiate, such as if they are a pulsar or part of a binary system. Slow-rotating and non-accreting neutron stars are almost undetectable; however, since the Hubble Space Telescope detection of RX J185635−3754 in the 1990s, a few nearby neutron stars that appear to emit only thermal radiation have been detected. Soft gamma repeaters are conjectured to be a type of neutron star with very strong magnetic fields, known as magnetars, or alternatively, neutron stars with fossil disks around them.Neutron stars in binary systems can undergo accretion which typically makes the system bright in X-rays while the material falling onto the neutron star can form hotspots that rotate in and out of view in identified X-ray pulsar systems. Additionally, such accretion can "recycle" old pulsars and potentially cause them to gain mass and spin-up to very fast rotation rates, forming the so-called millisecond pulsars. These binary systems will continue to evolve, and eventually the companions can become compact objects such as white dwarfs or neutron stars themselves, though other possibilities include a complete destruction of the companion through ablation or merger. The merger of binary neutron stars may be the source of short-duration gamma-ray bursts and are likely strong sources of gravitational waves. In 2017, a direct detection (GW170817) of the gravitational waves from such an event was observed, and gravitational waves have also been indirectly observed in a system where two neutron stars orbit each other.
Hello everyone.
I'm looking for an good equation of state for a neutron star, I'm starting with a degenerate neutron gas, but i have nothing to compare my results, I've search on the internet for it but haven't success. May you guys could have any graph of it to help me ?
Thanks a lot.
Hello to all. I've been trying to plot some graphs on Mathematica but I have faced some troubles so far.
I am working on this paper by Lattimer on binary systems:
https://arxiv.org/abs/astro-ph/0002203
I am trying to reproduce Figure 11 but something seems to go wrong.
Here's what I have...
Homework Statement
I'm doing a question from a past paper, preparing for an upcoming exam. There is no solutions so I was wondering if my answer is correct for all parts.
Take a star to be a uniform sphere with mass M_{i}=3.0 \times 10^{30} Kg and radius R_{i} = 7.0 \times 10^{8}m that...
I have heard that in neutron stars, the atoms do not repel nor do they attract. In a sense, could this mean that these atoms nucleuses could touch each other, or could the atoms touch in general?
[This thread was split from https://www.physicsforums.com/threads/a-light-wave-and-a-sound-wave-travelling-together.878450/#post-5518001 as it's an interesting topic in its own right]
That's actually an important point, in the core of neutron stars, the speed of sound increases with the...
Hi there,
I have a problem to solve in Cosmology which says:
"Write the formulas for the quantum kinetic energy of neutrons, protons and electrons as well as the formula for the gravitational energy for a neutron star that is comprised of free neutrons, protons and electrons in a ratio of Nn ...
Homework Statement
Homework Equations
rotational kinetic energy = 0.5 I ⋅ M ⋅ ω², where I is the moment of intertia, M the mass and ω the angular speed
The Attempt at a Solution
T = period of revolution
K = kinetic energy associated with rotational moviment
Since T increases with time...
So a programme that I watched on tv was talking about neutron stars and they said that the neutron stars neutrons were formed by protons and electrons combining to make neutrons. I was just wondering, how does this work, in the field of the quarks in the proton and how they are effected by an...
The Equivalence Principle says depicting gravity as a field associated with matter is equivalent to picturing it as twisting of space. Is there a space-twisting equivalent of a collapsed star as a shell of condensed matter with interior of intense gravitational field energy (found in the field...
How durable are the neutron stars, ie how long can they last? Will they "evaporate" like black holes or something else will happen with them after a very long period of time (eons)? Or are they immortal?
I'm asking because I have found nothing clear about the lifespan of a neutron star.
I am reading about mergers of a neutron star with a black hole and the association with GRB. While talking about the accretion disk, the paper I am reading says about the last stable circular orbit.
Firstly I thought it was where the Roche limit lies, where mass transfer or matter ejection from...
Now kindly pardon my ignorance but I hope one of you can explain to me how this can be possible.
A rotating neutron star or pulsar have been observed to spin at between 10 to 700 times per second. Now before I proceed further I like to draw your memories back to the merry go round we played as...
Hi everyone,
The charged particles in the magnetic field around the neuton star, is accelerated along the magnetic field lines, which would go in a curve, from the north pole to the south pole. Due to the acceleration the particles will emit radiation, along their movement axis, and because the...
Could neutron star jets with velocity greater than 0.9c be caused by a mix of ultra-relativistic core material escaping the star? See this link:
http://www.dailygalaxy.com/my_weblog/2015/08/neutron-star-jets-near-speed-of-light-rival-those-of-black-holes.html
Is there any good information about the chemical composition of relativistic jets from neutron stars? If the chemical composition of the jets was different from the accretion material it could shed light on the process that forms the jets.
OK so some stars evolve into neutron stars which I assume are so small (10's of kms) because ALL empty space is removed between the atoms.. absolute highest density possible?
Now.. is a black hole larger (massive and in diameter) than a neutron star and called a black hole only because the...
When a large amount of plasma radiates greatly while accreting on a magnetized neutron star, where does the radiation ultimately get its energy from, the magnetic field and/or gravitational field? Without doing the numbers, if the magnetic field does the work against the gravitational field, and...
If a bubble of quark type matter formed near the core of a magnetized neutron star, what would happen to its shape? Would it elongate along the magnetic field lines? Could it burst out of the magnetic poles of the star?
Hello all,
I could be looking at this the wrong way but here it goes:
From what I understand, if a star collapses into itself to form a neutron star, it would become more compact, denser and heavier with a larger gravitational attraction.
Now, if I understand correctly, the size of...
In calculations of quantities in Neutron stars with degenerate matter is usual to set temperature zero. If I'm right it means that pressure of this matter is negligible against pressure due to Pauli principle. But what about situation when the matter is in neutron star locally compressed. How...
Dear PF Forum,
I have question concerning neutron star and star just simply out of curiousity.
1. Can a star reach silicon burning stage then stop. It doesn't continue to iron burning stage.
2. Once a star reach iron burning stage, there's no stopping it to blast into supernova? Is supernova...
Dear PF Forum,
I've been searching the answer for this particular question about neutron star in google, but I don't find it, yet.
1. What is the temperature of a neutron star, right after it is formed from supernova?
2. Can anybody give me some timeline about neutron star cooling down?
3. What...
Dear PF forum.
Folks, what I have here may be an unimportant question. Still I'm curious to know the answer.
When iron fusion happens in a massive star, it will undergo supernova.
What I want to know is...
1. There are some binary (or perhaps ternary) neutron star systems.
Neturon star is...
I try to find answer to quite basic question.
Let's imagine neutron star and object with mass of 1 kg located far from the neutron star. Total energy of the object is ##E = U_g + mc^2##, for case when its velocity is zero and and ##U_g## is potential energy of gravitation.
The neutron star have...
Neutron stars are supposed to have an upper limit in mass, beyond which they collapse into perhaps a further type of degenerate matter or a singularity. There doesn't seem to be precisely defined upper limit, but the limit is estimated to be 1.5-3 solar masses. However, a hypothetical neutron...
The fastest moving pulsars are theoretically spinning neutron stars. They probably got their velocity from a kick from a supernova like Project Orion.
http://chandra.harvard.edu/photo/2012/igrj11014/
http://chandra.harvard.edu/photo/2003/b1957/closer_look.html
As I understand it, neutron stars...
Homework Statement
I am trying to answer the following question:
Among the animals that appear in the zoo of the Universe there are black holes and neutron stars. The mass of each of these is often the order of the mass of the Sun. The radius of a neutron star is about 10 km and a certain...
I have done large amounts of research and could not find any books, sites or forums of how the strange matter in strange stars is formed. I know that the process of the formation of the strange star carries out mostly like the collapse into neutron stars and quark stars but how do these strange...
I've gotten a bit confused about the creation of the neutron star/pulsar, so I was hoping someone could point me in the right direction :)
As fusion stops, when reaching the iron phase, the outer layers (hydrogen, helium, carbon... etc.) gets pulled in-wards do to gravity. This creates a bounce...
I had a question and I found a thread on PF with a nearly identical question ---Slowly add mass to a neutron star till it collapses. I learned some very interesting physics from that thread, namely the Tolman–Oppenheimer–Volkoff limit, and the significance of "9/8 of its Schwarzschild radius"...
Homework Statement
Exercise 2.6 (page 28)
Consider completely ionized matter consisting of hydrogen, helium, and heavier atomic species i>2. Let X and Y denote the fractions by mass of hydrogen and helium, respectively. Show that
\mu_e=\frac{2}{1+X}.
Approximate m_i=A_i m_u for all i, and...
Hi,
I am currently working on a Sci/Fi short story where a spaceship leaving a planet will perform a gravitational assist sling through a binary neutron star system. The problem is that I have difficulty finding information about how close a planet could be to a binary neutron star system? I...
This relates to a feat in a classic Thor comic. Thor is blasted by a Graviton Bomb and "is instantly subject to a gravimetric attraction akin to that of a neutron star.". He is then "pulled irresistibly down by the incalculable increase in local gravity and is quickly buried from view by an ever...
How would you approximately describe matter in the core of underlying neutron star? I am asking for really fundamental properties. No strange matter, consider just n,e,p. A ratio, can we describe particles as free? Gas x fluid x superfluid? etc.
Is this established or is it dependent on the size of the black hole?
http://www.space.com/22180-neutron-stars.html
Neutron stars pack their mass inside a 20-kilometer (12.4 miles) diameter. They are so dense that a single teaspoon would weigh a billion tons — assuming you somehow managed to...
1. The problem statement & given/known data
A neutron star is a collection of neutrons bound together by their mutual gravitation. The density of such a star is comparable to that of an atomic nucleus (10^17 kg/m^3).
a) Assuming the neutron star to be spherical in shape and of uniform mass...
As the title of the thread suggests, I'm interested in estimating the velocity distribution of neutrons in neutron star cores. Putting T ~ 10^12K gives v ~ 15%c or more under Boltzmann statistics. Could someone provide more information or a second opinion on this estimate? Thanks.
What would happen to a neutron star (on the cusp of becoming a black hole) if it were sped up to near the speed of light? Or more easily done, if I sped up to near the speed of light. Would the additional mass from the near light speed cause the neutron star to collapse in on itself and form a...
The question is attached.
I'm not sure how to approach to part (b).
The energy released could be in 3 forms, the rest mass energy for those matter ejected during supernova explosion, the binding energy released as the atomic structure changed, the ejected matter carries off some kinetic...
Here is my understanding, please correct me if I am wrong, thanks
At the end of the giant stage of a star, it experiences a supernova explosion, and turns into a neutron star (could be pulsar) or black hole, the explosion releases a lot of its matter.
Here is what I don't understand:
1...
Hi everyone!
First of all, I'm a brand new member and am looking forward to spending time on this forum, learning a bit more about science, and getting to know some of you.
Anyway, here's what's been on my mind lately:
I've heard that a thimbleful of neutron star material weighs as much as a...
Stimulated virtual W+, W- when supernova core--> neutron star?
Weak interactions allow supernova core electrons and protons to convert to neutrons and neutrinos allowing (under the right conditions) the formation of a neutron star? Large numbers virtual W+ and W-bosons are produced in a short...
Hi All,
I am preparing for PhD quals and have been looking at problems from other universities. I came across this one and am stumped on how to tackle it.
" Assume that the neutron density in a neutron star is 30.1/fm (that is 0.1 neutron per
cubic Fermi). Assuming T=0 and ignoring any...
Homework Statement
Suppose that an earth-mas object collides with a neutron star with radius 10 km and mass 1.4 $M_{sun}$. The material of the earth-like object would wrap around the neutron star and form a thin layer on top of the original neutron star surface. Assume the material gets...
How many neutrons are in a neutron star with a diameter of 42.0 km?
I was under the impression it was just
(42.0e3/1e-15)^3 = 7.0048e58
but that's wrong??
Homework Statement
The Crab Nebula is a cloud of glowing gas about 10 light-years across, located about 6500 light years from the Earth (the figure (Figure 1) ). It is the remnant of a star that underwent a supernova explosion, seen on Earth in 1054 a.d. Energy is released by the Crab Nebula...
I thought readers would be interested in this interesting article today on black hole and neutron star mergers and the very small possibility of instantaneous sterilization and extinction of all life on earth:http://www.space.com/22231-gamma-ray-bursts-neutron-stars.html...