If the mass of a star exceeds the Chandrasekhar limit , or 1.4 solar masses, when its nuclear fusion can no long sustain the pressure needed to counteract gravity, the star will supernova and collapse past the white dwarf stage, (as electron degeneracy pressure will not be enough to counter gravity) to the stage known as a neutron star.

If the stars mass exceeds three solar masses, then not even neutron degeneracy pressure will be enough to stop the star collapsing and a black hole will result. A typical neutron star will only have a radius of 10 kilometers, and be so dense that a teaspoon full will weigh about a billion tons.

At such huge densities the electrons are forced into the protons, reacting to form a neutron and a neutrino. In neutron star only 0.5 percent of the matter remains as protons and electrons, hence the name 'neutron star'. The material formed is actually 'fluid'; there is little force between neutrons to bind them together, it can't be a solid. It may in fact be a superfluid like liquid helium; The small residual amount of protons and electrons may allow this fluid to be superconducting also. Modeling material at this (and) higher densities is difficult, although direct observations by telescope of effects caused by processes in neutron stars will help prove or disprove the models.

The structure of neutron star is more similar to a planet like earth, than a star like our sun. There is an 'atmosphere' only a few centimeters thick, caused by evaporation of the surface material, then a solid crust, perhaps only a kilometer thick, followed by a mantle of solid and neutron superfluid, followed by a pure superfluid. It's hypothesized a massive example may even have a solid, crystalline core.

Types of neutron stars include Pulsars and Magnetars. Stephen Baxter has written a book about life inside a neutron star.
Science Fiction stories and books predominantly featuring a neutron star:
  • Neutron Star by Larry Niven - short story and title of book containing said story.
    Something got through the thought to be impervious General Products Hull created by the Puppeteers and killed the crew investigating Phssthpok's Star. A trouble shooter is sent to discover what it was. Like most of Niven's books, this one takes place in Known Space. The time frame is a few years before the Puppeteer Exodus.

    The neutron star has passing mention in Protector, but is not a key part of the story.

  • Flux by Stephen Baxter - Novel
    A branch of humanity has been engineered to exist in the curst of a neutron star. This neutron star is mentioned in passing in the book Ring, however it has no real value than mentioning other books in the same universe as Ring.

  • Dragon's Egg and Star Quake by Robert L. Forward - Novels
    Life on a neutron star. The speed of reactions taking place at the atomic and subatomic level is on the order of a million times faster than it is for molecular reactions - and thus life using this process lives about a million times faster. The life span of a cheela (about the size of a sesame seed and same mass as a human) is the same qualitative time, though it is possible to go through a generation or two of cheela in a single conversation.

Feel free to /msg me with additional titles.

A lot of the info in this node is sorta correct but not really correct so i will attempt to make it more accurate. What i know of neutron stars i have learned from my time as an astro-physics major and while i still don't have the physics to understand a neutron star i am very familiar with the concepts.

First off there are many ways to form a neutron star not just supernova, although the supernova is the most common. When a star is in its latter stages of life it has a small core which is layered. The outer layer is burning hydrogen, the helium, then there is a jumbled of oxygen neon and carbon and others. Eventually the star stars to run out of the fuel in the center which is normally silicon. The silicon fuses to make iron which cannot be fused to make more energy. Iron is a dead end. The stars energy source is shut off. Now the core cools and contracts very fast. It takes about a tenth of a second. The energy release from this contraction photodisintegrates much of the iron. Neutronization then begins in the dense core forcing electrons into protons forming neutrons. Atoms break down into just balls of neutron. After about a quater of a second the core is solid neutrons and can be contracted no more the layers that were moving downward as fast as 15% of the spped of light bounce off the now solid core. This bounce is the shockwave which causes the supernova. As it travels throught the star it is like a tidl wave of almost infinite size and energy. This shockwave and the flood of neutrinos from the neutronization force the energy outward blowing off the less dense outer layers in a supernova.

What we have left is a neutron star. This star will have to have a mass of more than 1.4 solar masses and less than 3 solar masses. (the upper limits of the neutron star's mas are uncertain due to uncertainties in the strength of the strong electric force.)

The neutron star has a radius of about 10-15 kilometers. The inner 10 meters radius is a superfluid and superconductive soup of protons and neutrons. on thsi floats a kilometer or so o superfluid neutrons and the top is a crust of neutrons. (This is the most up to date model. THis is an area of current research and there is uncertainty about the interior of a neutron star.)

Ok, i am done for now, anything else you want added to this /msg me. Enjoy :)

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