A neutron star is formed from the collapsed remnant of a massive star; i. Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth e. a Type II, Type Ib or Type Ic supernova. Type II Supernova, or core-collapse supernova, is a sub-category of cataclysmic Variable stars that results from the internal collapse and violent explosion Types Ib and Ic supernovae are categories of stellar explosions A supernova (plural supernovae or supernovas) is a stellar Explosion. Models predict that neutron stars consist mostly of neutrons, hence the name. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Such stars are very hot, as supported by the Pauli exclusion principle indicating repulsion between neutrons. The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925 A neutron star is one of the few possible conclusions of stellar evolution. In Astronomy, the term compact star (sometimes compact object) is used to refer collectively to White dwarfs Neutron stars other exotic Stellar evolution is the process by which a Star undergoes a sequence of radical changes during its lifetime

A typical neutron star has a mass between 1.35 and about 2.1 solar masses, with a corresponding radius between 20 and 10 km,^[1] respectively — in contrast, the Sun is 30,000 to 70,000 times larger. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object To help compare different orders of magnitude, the following list describes various Mass levels between 10&minus36&thinsp kg and 1053&thinspkg The solar mass is a standard way to express Mass in Astronomy, used to describe the masses of other Stars and galaxies. Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand The Sun (Sol is the Star at the center of the Solar System. Thus, neutron stars have overall densities of 8.4×10¹⁶ to 1×10¹⁸ kg/m³,^[2] which compares with the approximate density of an atomic nucleus of 3×10¹⁷ kg/m³. CM3 redirects here If you were looking for the 3rd game in the Cooking Mama series abbreviated as CM3 see here. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom ^[3] The neutron star's density varies from below 1×10⁹ kg/m³ in the crust increasing with depth to above 6 or 8×10¹⁷ kg/m³ deeper inside. ^[4]

In general, compact stars of less than 1. 44 solar masses, the Chandrasekhar limit, are white dwarfs; above 2 to 3 solar masses (the Tolman-Oppenheimer-Volkoff limit), a quark star might be created, however this is uncertain. The Chandrasekhar limit limits the mass of bodies made from Electron-degenerate matter, a dense form of matter which consists of nuclei immersed in a gas of Electrons A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. The Tolman-Oppenheimer-Volkoff ( TOV) limit is an upper bound to the mass of stars composed of neutron-degenerate matter ( Neutron stars. A quark star or strange star is a hypothetical type of Exotic star composed of Quark matter, or Strange matter. Gravitational collapse will always occur on any star over 5 solar masses, inevitably producing a black hole. Gravitational collapse in Astronomy is the inward fall of a massive body under the influence of the force of Gravity. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e

Formation

As the core of a massive star is compressed during a supernova, and collapses into a neutron star, it retains most of its angular momentum. A supernova (plural supernovae or supernovas) is a stellar Explosion. In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position Since it has only a tiny fraction of its parent's radius (and therefore its moment of inertia is sharply reduced), a neutron star is formed with very high rotation speed, and then gradually slows down. This article is about the moment of inertia of a rotating object. Neutron stars are known to have rotation periods between about 1. 4ms to thirty seconds. The neutron star's compactness also gives it very high surface gravity, 2×10¹¹ to 3×10¹² times stronger than that of Earth. The surface gravity, g, of an astronomical or other object is the Gravitational acceleration experienced at its surface EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 One measure of such immense gravity is the fact that neutron stars have an escape velocity of around 150,000 km/s, about 50% of the speed of light. In Physics, escape velocity is the speed where the Kinetic energy of an object is equal to the magnitude of its Gravitational potential energy To help compare different Orders of magnitude, the following list describes various Speed levels between 1 Matter falling onto the surface of a neutron star would be super-accelerated by this gravity and the force of impact would likely destroy the object's component atoms, rendering all its matter identical, in most respects, to the rest of the star.

Structure

A model of a neutron star's internal structure

Current understanding of the structure of neutron stars is defined by existing mathematical models, but it might be possible to infer through studies of neutron-star oscillations. Asteroseismology studies the internal structure of our Sun and other stars using oscillations Similar to asteroseismology for ordinary stars, the inner structure might be derived by analyzing observed frequency spectra of stellar oscillations. Asteroseismology (from Greek grc ἀστήρ astēr, "star" grc σεισμός seismos, "earthquake" and grc -λογία Familiar concepts associated with a Frequency are colors musical notes radio/TV channels and even the regular rotation of the earth A neutron star is so dense that one teaspoon (5 millilitre) of its material would have a mass over 5×10¹² kg. The pages linked in the right-hand column contain lists of volumes that are of the same order of magnitude (power of ten The litre or liter (see spelling differences) is a unit of Volume. ^[5] On the basis of current models, the matter at the surface of a neutron star is composed of ordinary atomic nuclei as well as electrons. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The "atmosphere" of the star is roughly one meter thick, below which one encounters a solid "crust". Proceeding inward, one encounters nuclei with ever increasing numbers of neutrons; such nuclei would decay quickly on Earth, but are kept stable by tremendous pressures. Proceeding deeper, one comes to a point called neutron drip where free neutrons leak out of nuclei. The neutron drip line is a concept in particle and Nuclear physics. In this region, there are nuclei, free electrons, and free neutrons. The nuclei become smaller and smaller until the core is reached, by definition the point where they disappear altogether. The exact nature of the superdense matter in the core is still not well understood. While this theoretical substance is referred to as neutronium in science fiction and popular literature, the term "neutronium" is rarely used in scientific publications, due to ambiguity over its meaning. Neutronium is a term originally used in Science fiction and in popular literature to refer to an extremely Dense phase of matter composed primarily of The term neutron-degenerate matter is sometimes used, though not universally as the term incorporates assumptions about the nature of neutron star core material. Degenerate matter is matter which has sufficiently high Density that the dominant contribution to its Pressure rises from the Pauli Exclusion Neutron star core material could be a superfluid mixture of neutrons with a few protons and electrons, or it could incorporate high-energy particles like pions and kaons in addition to neutrons, or it could be composed of strange matter incorporating quarks heavier than up and down quarks, or it could be quark matter not bound into hadrons. Superfluidity is a phase of matter or description of Heat capacity in which unusual effects are observed when Liquids, typically of Helium-4 The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive In Particle physics, pion (short for pi meson) is the collective name for three Subatomic particles, and. In Particle physics, a kaon (/ˈkeɪɒn/ also called K-meson and denoted) is any one of a group of four Mesons distinguished by the fact that they For the physics concept see Strange matter. Strange Matter is a Children's book series created by Marty M In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The up quark is a particle described by the Standard Model theory of Physics. The down quark is a first-generation Quark with a charge of -(1/3 e. Quark matter or QCD matter (see QCD) refers to any of a number of theorized phases of matter whose degrees of freedom include Quarks and Gluons In Particle physics, a hadron ( from the ἁδρός hadrós, " stout, thick " ( (A compact star composed entirely of strange matter would be called a strange star. A quark star or strange star is a hypothetical type of Exotic star composed of Quark matter, or Strange matter. ) However, so far, observations have neither indicated nor ruled out such exotic states of matter.

History of discoveries

The first direct observation of a neutron star in visible light. The neutron star is RX J185635-3754. RX J18565-3754 (also called RX J185635-3754, RX J185635-375, and various other designations is a nearby Neutron star.

In 1932, Sir James Chadwick discovered the neutron as an elementary particle,^[6] for which he was awarded the Nobel Prize in Physics in 1935. Sir James Chadwick, CH (20 October 1891 &ndash 24 July 1974 was an English Physicist and Nobel laureate in physics awarded for his discovery of the The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences.

In 1933, Walter Baade and Fritz Zwicky proposed the existence of the neutron star,^[7] only a year after Chadwick's discovery of the neutron. Biography Along with Fritz Zwicky, he proposed that Supernovae could create Neutron stars He took advantage of wartime blackout conditions during Fritz Zwicky ( February 14 1898 &ndash February 8 1974) was an American-based Swiss Astronomer of Bulgarian origin In seeking an explanation for the origin of a supernova, they proposed that the neutron star is formed in a supernova. A supernova (plural supernovae or supernovas) is a stellar Explosion. Supernovae are suddenly appearing dying stars in the sky, whose luminosity in the optical might outshine an entire galaxy for days to weeks. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter Baade and Zwicky correctly proposed at that time that the release of the gravitational binding energy of the neutron stars powers the supernova: "In the supernova process mass in bulk is annihilated". The Gravitational Binding energy of an object consisting of loose material held together by gravity alone is the amount of Energy required to pull all If the central part of a massive star before its collapse contains (for example) 3 solar masses, then a neutron star of 2 solar masses can be formed. The binding energy E of such a neutron star, when expressed in mass units via the mass-energy equivalence formula E = mc², is 1 solar mass. In Physics, mass–energy equivalence is the concept that for particles slower than light any Mass has an associated Energy and vice versa. It is ultimately this energy that powers the supernova.

In 1965, Antony Hewish and Samuel Okoye discovered "an unusual source of high radio brightness temperature in the Crab Nebula". Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for The Crab Nebula  (catalogue designations M 1 NGC 1952 Taurus A is a Supernova remnant and Pulsar wind nebula in the Constellation ^[8] This source turned out to be the Crab Nebula neutron star that resulted from the great supernova of 1054 CE. The Crab Pulsar (PSR B0531+21 is a relatively young Neutron star. SN 1054 (Crab Supernova was a Supernova that was widely seen on Earth in the year 1054

In 1967, Jocelyn Bell and Antony Hewish discovered regular radio pulses from the location of the Hewish and Okoye radio source. Dame Jocelyn Bell Burnell, DBE, FRS, FRAS (born Susan Jocelyn Bell on 15 July 1943) is an astrophysicist Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for This pulsar was later interpreted as originating from an isolated, rotating neutron star. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves The energy source of the pulsar is the rotational energy of the neutron star. The largest number of known neutron stars are of this type (See Rotation-powered pulsar). Rotation-powered pulsar is one of the major classes of Pulsars A Rotation-powered pulsar is a rapidly rotating Neutron star, whose Electromagnetic

In 1971, Riccardo Giacconi, Herbert Gursky, Ed Kellogg, R. Riccardo Giacconi (born October 6, 1931) is an Italian-born American Nobel Prize -winning Astrophysicist. Levinson, E. Schreier, and H. Tananbaum discovered 4. 8 second pulsations in an X-ray source in the constellation Centaurus, Cen X-3. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Centaurus ( Centaur) is a bright constellation of the southern hemisphere. They interpreted this as resulting from a rotating hot neutron star. The energy source is gravitational and results from a rain of gas falling onto the surface of the neutron star from a companion star or the interstellar medium (See Accretion-powered pulsar). A binary star is a Star system consisting of two Stars orbiting around their Center of mass. X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity

In 1974, Antony Hewish was awarded the Nobel Prize in Physics "for his decisive role in the discovery of pulsars" without Samuel Okoye and Jocelyn Bell who shared in the discovery. Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. Dame Jocelyn Bell Burnell, DBE, FRS, FRAS (born Susan Jocelyn Bell on 15 July 1943) is an astrophysicist

Rotation

Neutron stars rotate extremely rapidly after their creation due to the conservation of angular momentum; like a spinning ice skater pulling in his or her arms, the slow rotation of the original star's core speeds up as it shrinks. A newborn neutron star can rotate several times a second; sometimes, when they orbit a companion star and are able to accrete matter from it, they can increase this to several hundred times per second, distorting into an oblate spheroid shape despite their own immense gravity (an equatorial bulge). A millisecond pulsar ( MSP) often referred to as "recycled pulsar", is a Pulsar with a rotational period in the range of about 1-10 Milliseconds An oblate Spheroid is a rotationally symmetric Ellipsoid having a polar axis shorter than the diameter of the equatorial circle whose plane An equatorial bulge is a bulge which a planet may have around its Equator, distorting it into an Oblate spheroid.

Over time, neutron stars slow down because their rotating magnetic fields radiate energy; older neutron stars may take several seconds for each revolution.

The rate at which a neutron star slows down its rotation is usually constant and very small: the observed rates are between 10^-10 and 10^-21 second for each rotation. In other words, for a typical slow down rate of 10^-15 seconds per rotation, then a neutron star now rotating in 1 second will rotate in 1. 000003 seconds after a century, or 1. 03 seconds after 1 million years.

Sometimes a neutron star will spin up or undergo a glitch, a rapid and unexpected increase of its rotation speed (of the same, extremely small scale as the constant slowing down). Glitches are thought to be the effect of a starquake: As the rotation of the star slows down, the shape becomes more spherical. Due to the stiffness of the 'neutron' crust, this happens as discrete events as the crust ruptures, similar to tectonic earthquakes. After the starquake, the star will have a smaller equatorial radius, and since angular momentum is conserved, rotational speed increases. Recent work, however, suggests that a starquake would not release sufficient energy for a neutron star glitch; it has been suggested that glitches may instead be caused by transitions of vortices in the superfluid core of the star from one metastable energy state to a lower one. ^[9]

Neutron stars may "pulse" due to particle acceleration near the magnetic poles, which are not aligned with the rotation axis of the star. Through mechanisms not yet entirely understood, these particles produce coherent beams of radio emission. External viewers see these beams as pulses of radiation whenever the magnetic pole sweeps past the line of sight. The pulses come at the same rate as the rotation of the neutron star, and thus, appear periodic. Neutron stars which emit such pulses are called pulsars. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves

The most rapidly rotating neutron star currently known, PSR J1748-2446ad, rotates at 716 revolutions per second. |-! style="background-color #FFFFC0" colspan="2" | Astrometry|- style="vertical-align top"| Distance | 18 ^[10] A recent paper reported the detection of an X-ray burst oscillation (an indirect measure of spin) at 1122 Hz from the neutron star XTE J1739-285. ^[11] However, at present this signal has only been seen once, and should be regarded as tentative until confirmed in another burst from this star.

Population and distances

At present there are about 2000 known neutron stars in the Milky Way and the Magellanic Clouds, the majority of which have been detected as radio pulsars. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply History The Magellanic Clouds were certainly known since the earliest times by the ancient Middle Eastern peoples Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves The population of neutron stars is concentrated along the disk of the Milky Way although the spread perpendicular to the disk is fairly large. The reason for this spread is that neutron stars are born with high speeds (400 km/s) as a result of an imparted momentum-kick from an asymmetry during the supernova explosion process. A supernova (plural supernovae or supernovas) is a stellar Explosion. The closest known neutron star is RX J185635-3754 which is presently at a distance of about 200 light years and which is expected to pass as close as 170 light years in approximately 300,000 years. RX J18565-3754 (also called RX J185635-3754, RX J185635-375, and various other designations is a nearby Neutron star. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by This neutron star is also one of a few that lack a binary companion.

Binary neutron stars

About 5% of all neutron stars are members of a binary system. A binary system is an astronomical term referring to two objects in space (usually Stars but also Planets galaxies or Asteroids which The formation and evolution scenario of binary neutron stars is a rather exotic and complicated process^[12]. The companion stars may be either ordinary stars, white dwarfs or other neutron stars. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. According to modern theories of binary evolution it is expected that neutron stars also exist in binary systems with black hole companions. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e Such binaries are expected to be prime sources for emitting gravitational waves. In Physics, a gravitational wave is a Fluctuation in the Curvature of Spacetime which propagates as a wave, traveling outward from Neutron stars in binary systems often emit X-rays which is caused by the heating of material (gas) accreted from the companion star. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. Material from the outer layers of a (bloated) companion star is sucked towards the neutron star as a result of its very strong gravitational field.

Subtypes

• Neutron star
  • Radio-quiet neutron stars
  • Radio emitting
    • Single pulsars – general term for neutron stars that emit directed pulses of radiation towards us at regular intervals (due to their strong magnetic fields). A radio-quiet neutron star is a Neutron star that does not seem to emit radio emissions like most other neutron stars. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves
      • Rotation-powered pulsar ("radio pulsar")
        • Magnetar – a neutron star with an extremely strong magnetic field (1000 times more than a regular neutron star), and long rotation periods (5 to 12 seconds). Rotation-powered pulsar is one of the major classes of Pulsars A Rotation-powered pulsar is a rapidly rotating Neutron star, whose Electromagnetic A magnetar is a Neutron star with an extremely powerful Magnetic field, the decay of which powers the emission of copious amounts of high-energy Electromagnetic
          • Soft gamma repeater
          • Anomalous X-ray pulsar
    • Binary pulsars
      • Accretion-powered pulsar ("X-ray pulsar")
        • X-ray burster – a neutron star with a low mass binary companion from which matter is accreted resulting in irregular bursts of energy from the surface of the neutron star. A soft gamma repeater ( SGR) is an astronomical object which emits large bursts of Gamma rays and X-rays at irregular intervals Anomalous X-ray Pulsars ( AXP s are now widely believed to be Magnetars mdashyoung isolated highly magnetized Neutron stars These energtic X-ray A binary pulsar is a Pulsar with a binary companion, often another Pulsar, White dwarf or Neutron star. X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity X-ray bursters are a class of binary stars which have periodic outbursts luminous in X-rays.
        • Millisecond pulsar ("recycled pulsar")
    • Quark Star – a currently still hypothetical type of neutron star composed of quark matter, or strange matter. A millisecond pulsar ( MSP) often referred to as "recycled pulsar", is a Pulsar with a rotational period in the range of about 1-10 Milliseconds A quark star or strange star is a hypothetical type of Exotic star composed of Quark matter, or Strange matter. Quark matter or QCD matter (see QCD) refers to any of a number of theorized phases of matter whose degrees of freedom include Quarks and Gluons For the physics concept see Strange matter. Strange Matter is a Children's book series created by Marty M As of 2008, there are three candidates.
    • Preon star – a currently still hypothetical type of neutron star composed of preon matter. A preon star is a hypothetical Compact star made of Preons a group of Theoretical Subatomic particles that may compose Quarks In Particle physics, preons are postulated "point-like" particles conceived to be subcomponents of Quarks and Leptons The word was coined As of 2008, there is no evidence for the existence of preons. In Particle physics, preons are postulated "point-like" particles conceived to be subcomponents of Quarks and Leptons The word was coined

Giant nuclei

A neutron star has some of the properties of an atomic nucleus, including density, and being made of nucleons. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In Physics a nucleon is a collective name for two Baryons the Neutron and the Proton. In popular scientific writing, neutron stars are therefore sometimes described as giant nuclei. However, in other respects, neutron stars and atomic nuclei are quite different. In particular, a nucleus is held together by the strong force, while a neutron star is held together by gravity. In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Gravitation is a natural Phenomenon by which objects with Mass attract one another It is generally more useful to consider such objects as stars. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth

See also

References

External links

• Introduction to neutron stars
• "NASA Sees Hidden Structure Of Neutron Star In Starquake". SpaceDaily. com. April 26 2006
• "Mysterious X-ray sources may be lone neutron stars". Events 1467 - The miraculous image in Our Lady of Good Counsel appear in Genazzano, Italy. New Scientist.
• "Massive neutron star rules out exotic matter". New Scientist. According to a new analysis, exotic states of matter such as free quarks or BECs do not arise inside neutron stars.
• "Neutron star clocked at mind-boggling velocity". New Scientist. A neutron star has been clocked traveling at more than 1500 kilometers per second.