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.
Sorry, the equations are messy. I already know the answer to the actual homework problem, but I don't really know why certain terms are neglected.
I know that the equation will only include the volume term, symmetry term and the extra added gravity term. I just want to understand why
I know...
I was listening to a Star Date podcast regarding the constellation Vulpecula and learned about the discovery of pulsars and neutron stars.
https://stardate.org/radio/program/2023-03-19
The first neutron star was discovered in Vulpecula in 1967.
https://en.wikipedia.org/wiki/PSR_B1919+21
In...
When we read about the mass transfer between neutron star pairs in a binary system, how is it that the one receiving the matter can increase its spin rate. Adding mass to a spinning object ought to slow due to conservation of momentum. Where does the energy come from?
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My math is very weak and I don't like explanations done using math. I read books with very little math. I try to use reason based on what I've read. My understanding is time slows down in gravity and it will actually stop at the event horizon (see...
Here is a presentation on the discovery of two colliding neutron stars and the resulting phenomena such as gravity waves, gamma ray bursts, and synthesis of high atomic number elements. The author is a theoretical physicist who is involved in the research.
He says that the neutron stars most...
I have a rudimentary understanding of classical physics and some (lesser) level of relativity and quantum mechanics. All came from undergrad studies before most of you were born. I tried to jump into the quantum world, only to find it necessary to relearn the basics of maxwells equations and...
Since electromagnetic radiation is emitted as electrons decay from higher to lower states of excitation, I would assume that neutron stars cannot lose energy by blackbody radiation. That would leave tidal drag and evaporation as the only ways a neutron star can lose energy...True?
Hello.
I'm very interested to find out more about the maximum masses of white dwarf stars and of neutron stars. Please note that while my level in this forum is Basic, I am familiar with the role that the Chandrasekhar limit has played in our understanding of white dwarves. I was therefore...
I've just watched a vid about jets of matter and neutron stars. It was stated in it that a neutron star is a star that's been compressed from say a sun sized star to the size of a city, every thing OK upto now. Then it goes on to say that it has, the neutron star, enormous gravity, this is were...
From, https://www.syfy.com/syfywire/wham-bullseye-galactic-collision-creates-a-ring-of-black-holes-and-neutron-stars
..."“So you have a nice, normal spiral galaxy, right, just out there doing its thing, when BAM! A smaller galaxy careens right through the middle of it like a bullet! Chaos...
Hello everyone.
I'm currently working on NS mass relations and trying to plot a curve with predicted masses-radii and observations on NS.
There are some free data at this website: http://xtreme.as.arizona.edu/NeutronStars/index.php/neutron-star-radii/ . I downloaded the .tar file and tried to...
Some new papers appeared about processes in the collision of the two neutron stars, measured in August 2017.
Is now more clear, why 2 second delay between gamma rays and gravitational waves happens?
From Wikipedia:
Quark-degenerate matter may occur in the cores of neutron stars, depending on the equations of state of neutron-degenerate matter. It may also occur in hypothetical quark stars, formed by the collapse of objects above the Tolman–Oppenheimer–Volkoff mass limit for...
Has anyone else heard of that gravity waves may be the result of another type of supernova remains, called a Grav-Star? It seems almost to physically mimic a neuron star but stopped just shy of becoming a black hole, yet it still has enough of a gravity well to prevent light from escaping. Is...
The sources I've looked at claim the magnetic field is present because there are still some electrons in the neutron star.
Here is how I understand their reasoning: a star's radius significantly decreases when it collapses into a neutron star, ultimately decreasing its moment of inertia. In...
How does one determine/calculate the masses, orbital period, and separation of two merging neutron stars from the characteristics of its gravity wave LIGO signal? And how does this information allow one to calculate the distance to the galaxy that housed the merger? And how can one calculate...
I have a sci-fi idea regarding being able to move planets around like billiard balls.
I'm theorizing that, after a nova, some of the bands of material around a star formed a new ring of rocky planets around a Neutron Star. Naturally, these are bathed in radiation.
Having never taken high...
I read an article today stating that the possible explanation for the near total absence of heavier elements such as gold and uranium in many galaxies may be due to those galaxies not forming around a central black hole that has in absorbing one or more neutron stars causing fusion of neutrons...
Rumors are starting to fly that LIGO/VIRGO sees a signal of merging neutron stars, with an optical counterpart. Indeed, the thing that seems to have triggered the rumors was having a number of telescopes suddenly pointing at the same patch of sky.
It's difficult to discuss the science behind...
Before today, I'd been led to believe that collections of only one (or few) types of matter could never exist: And to my surprise it is indeed possible to have degenerate matter, resulting from the death of less massive stars! So I'm curious: If these lesser massive stars collapse due to their...
I was just wondering if there is anything to suggest that black holes are anything but giant neutron stars cloaked in an event horizon created by their own gravity. I mean if a neutron star is just on the cusp of having enough mass to be a black hole, and then gains that mass, what's to say it...
Do neutron stars have a minimum volume? Anything "in the way" of perhaps baseball sized neutron star? Or would something like that be an impossibility?
How neat to have one in a laboratory...or not lol
I know there is theoretical possibility of making mini black holes in particle acclerators, but what about mini neutron stars, or even mini quark stars?
I realize the neutron decays in 15 mins if left all alone. What is the minimum number of neutrons needed inside a nuclei for it to be stable...
Some observed neutron stars rotate hundreds of times per second. Speeds at the surface of these stars are as much as 15% the speed of light. These huge speeds are generated because angular momentum is conserved when a large rotating pre-super nova star collapses into a neutron star.
The...
I was wondering if a binary system of neutron stars were to collide what kind of nova or supernova would it be. Is it different if the final mass of the neutron star is sufficient enough for a black hole or if it still a neutron star?
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?
Homework Statement
Calculate the number of white dwarf, neutron star and black holes the galaxy will have after 5Gyr of evolution.
M<8(solar mass) for white dwarf
8(solar mass) < M < 40(solar mass) for neutron star
M > 40(solar mass) for black hole
Initial mass function is ξ(M) = AM-s...
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.
I'm trying to derive the formula for the characteristic age of a pulsar.
What I'm starting with is the following differential equation.
dP/dt=K*P2-n
What i think is odd, is several places they say solving this differential equation gives the following solution...
A method of definitely distinguishing a neutron star from a possible stellar black hole is that it produces X-ray bursts, which have a sharp rise time and may last for an extended period. I had previously thought these occurred when hydrogen fell to the surface and was immediately fused to...
I think this could be a good chance that we see how neutron stars form from White Dwarf mergers. The combined mass of the two are less that than required for a type Ia Supernovae. Won't they merge and collapse into a neutron star? What does everyone else think might happen. I want to be sure if...
In a neutron star gravity has overcome electron degeneracy pressure allowing the protons and electrons to combine into neutrons. But if that is the case, how do neutrons emit light if there are no electrons to swoosh the photons away?
I have been thinking, and wonder if the surface (or "crust")...
If they are so insanely dense and their gravity is so mind-numbingly great, what prevents a neutron star from immediately collapsing into a black hole?
Do neutron star, pulsars, magnetars etc. have solar flares like the sun or do they have sun spots like the sun or do they have solar winds and if they do have any of those types of weather, what are they called?
I saw a thread that asked the same basic question as I'm asking, but the explanation was beyond my current knowledge. Please consider answering my question as if you were being interviewed for a Discovery Channel special and had to make it comprehensible for a general audience. Thanks!
For me...
When matter is crushed in a neutron star are the atoms of molecules closer and the electrons are the same distance from the nucleus, or is the electron cloud closer to the nucleus? If the latter, how is this possible if the orbits have to have fixed orbitals due to the standing waves of the...
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...
Hi,
I was reading about free neutron beta decay the other day and it came to me the idea of neutron stars. As I understand, neutron stars are held together by gravity instead of strong force interaction (which I think is the mechanism that gives stability to neutron in common nuclei). So one...
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...
Hi, PF:
I'm currently about to graduate from my Ph. D. program in Physics and I want to focus my research in theoretical physics. I feel very excited by topics such as Astrophysics and GR, but also low temperature physics, such as superconductivity, bose-einstein condensation, superfluidity...
So, I was disappointed to find out that the surface of a neutron star is at 1 million kelvin, not 100 billion kelvin. I did some calculations a while back using the 100 billion K as a temperature (the core temperature of a neutron star), and found that it would be emitting more radiation than...
Yesterday, I read about Hawking's new proposal regarding the firewall paradox.
A more general thought about standard black holes occurred to me. Black holes including stellar black holes are of course always presented as if the event horizon is an invisible barrier, which the unfortunate...
So how much denser than is a neutron star than an atom? Is it called a neutron star because electron's orbital effect no longer exists/acts the same, so as to no longer cause 99.99% of everything to be space?
Simply put, either by chance or a suicidal type-III Civilization, 2 neutron stars, or a neutron star an a large-ish main sequence star are thrown at each other and fall STRAIGHT into each other.
What happens? Does the ~1.4 C Newtonian impact speed result in them getting blown up and releasing...
Dear all,
I'm starting to study neutron star accretion and a lot of physical phoenomena coming from different scales come along and a consistent picture is frankly hard to grasp.
But for now, a real mind boggling question can't exit my mind.
Are Neutron stars, as a whole Quantum, or...