Neutron star

Once formed, neutron stars no longer actively generate heat and cool over time, but they may still evolve further through collisions or accretion. Most of the basic models for these objects imply that they are composed almost entirely of neutrons, as the extreme pressure causes the electrons and protons present in normal matter to combine producing neutrons. These stars are partially supported against further collapse by neutron degeneracy pressure, just as white dwarfs are supported against collapse by electron degeneracy pressure. However, this is not by itself sufficient to hold up an object beyond 0.7 M_☉^[4][5] and repulsive nuclear forces play a larger role in supporting more massive neutron stars.^[6][7] If the remnant star has a mass exceeding the Tolman–Oppenheimer–Volkoff limit, which ranges from 2.2–2.9 M_☉, the combination of degeneracy pressure and nuclear forces is insufficient to support the neutron star, causing it to collapse and form a black hole. The most massive neutron star detected so far, PSR J0952–0607, is estimated to be 2.35±0.17 M_☉.^[8]

Newly formed neutron stars may have surface temperatures of ten million K or more. However, since neutron stars generate no new heat through fusion, they inexorably cool down after their formation. Consequently, a given neutron star reaches a surface temperature of one million degrees K when it is between one thousand and one million years old.^[9] Older and even-cooler neutron stars are still easy to discover. For example, the well-studied neutron star, RX J1856.5−3754, has an average surface temperature of about 434,000 K.^[10] For comparison, the Sun has an effective surface temperature of 5,780 K.^[11]

Neutron star material is remarkably dense: 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-kilometer chunk of the Earth (a cube with edges of about 800 meters) from Earth's surface.^[12][13]

As a star's core collapses, its rotation rate increases due to

There are thought to be around one billion neutron stars in the Milky Way,^[16] and at a minimum several hundred million, a figure obtained by estimating the number of stars that have undergone supernova explosions.^[17] However, many of them have existed for a long period of time and have cooled down considerably. These stars radiate very little electromagnetic radiation; 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 a part of a binary system. Slow-rotating and non-accreting neutron stars are difficult to detect, due to the absence of electromagnetic radiation; however, since the Hubble Space Telescope's detection of RX J1856.5−3754 in the 1990s, a few nearby neutron stars that appear to emit only thermal radiation have been detected.

Neutron stars in binary systems can undergo accretion, in which case they emit large amounts of

Any

As the core of a massive star is compressed during a Type II supernova or a Type Ib or Type Ic supernova, and collapses into a neutron star, it retains most of its angular momentum. Because it has only a tiny fraction of its parent's radius (sharply reducing its moment of inertia), a neutron star is formed with very high rotation speed and then, over a very long period, it slows. Neutron stars are known that have rotation periods from about 1.4 ms to 30 s. The neutron star's density also gives it very high surface gravity, with typical values ranging from 10¹² to 10¹³ m/s² (more than 10¹¹ times that of Earth).^[21] One measure of such immense gravity is the fact that neutron stars have an escape velocity of over half the speed of light.^[22] The neutron star's gravity accelerates infalling matter to tremendous speed, and tidal forces near the surface can cause spaghettification.^[22]

Properties

Mass and temperature

A neutron star has a mass of at least 1.1 solar masses (M_☉).^[23] The upper limit of mass for a neutron star is called the

The temperature inside a newly formed neutron star is from around 10¹¹ to 10¹² kelvin.^[29] However, the huge number of neutrinos it emits carries away so much energy that the temperature of an isolated neutron star falls within a few years to around 10⁶ kelvin.^[29] At this lower temperature, most of the light generated by a neutron star is in X-rays.

Some researchers have proposed a neutron star classification system using Roman numerals (not to be confused with the Yerkes luminosity classes for non-degenerate stars) to sort neutron stars by their mass and cooling rates: type I for neutron stars with low mass and cooling rates, type II for neutron stars with higher mass and cooling rates, and a proposed type III for neutron stars with even higher mass, approaching 2 M_☉, and with higher cooling rates and possibly candidates for exotic stars.^[30]

Density and pressure

Neutron stars have overall densities of 3.7×10¹⁷ to 5.9×10¹⁷ kg/m³ (2.6×10¹⁴ to 4.1×10¹⁴ times the density of the Sun),

The equation of state of matter at such high densities is not precisely known because of the theoretical difficulties associated with extrapolating the likely behavior of quantum chromodynamics, superconductivity, and superfluidity of matter in such states. The problem is exacerbated by the empirical difficulties of observing the characteristics of any object that is hundreds of parsecs away, or farther.^[33] Neutron stars are thought to have high rigidity in the crust, and thus a low Love number.^[34][35]

A neutron star has some of the properties of an atomic nucleus, including density (within an order of magnitude) and being composed of nucleons. 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. A nucleus is held together by the strong interaction, whereas a neutron star is held together by gravity. The density of a nucleus is uniform, while neutron stars are predicted to consist of multiple layers with varying compositions and densities.^[36]

Magnetic field

The magnetic field strength on the surface of neutron stars ranges from c. 10⁴ to 10¹¹ 

The origins of the strong magnetic field are as yet unclear.[37] One hypothesis is that of "flux freezing", or conservation of the original magnetic flux during the formation of the neutron star.^[37] If an object has a certain magnetic flux over its surface area, and that area shrinks to a smaller area, but the magnetic flux is conserved, then the magnetic field would correspondingly increase. Likewise, a collapsing star begins with a much larger surface area than the resulting neutron star, and conservation of magnetic flux would result in a far stronger magnetic field. However, this simple explanation does not fully explain magnetic field strengths of neutron stars.^[37]

Gravity and equation of state

The gravitational field at a neutron star's surface is about 2×10¹¹ times stronger than on Earth, at around 2.0×10¹² m/s².^[44] Such a strong gravitational field acts as a gravitational lens and bends the radiation emitted by the neutron star such that parts of the normally invisible rear surface become visible.^[43] If the radius of the neutron star is 3GM/c² or less, then the photons may be trapped in an orbit, thus making the whole surface of that neutron star visible from a single vantage point, along with destabilizing photon orbits at or below the 1 radius distance of the star.

A fraction of the mass of a star that collapses to form a neutron star is released in the supernova explosion from which it forms (from the law of mass–energy equivalence, E = mc²). The energy comes from the gravitational binding energy of a neutron star.

Hence, the gravitational force of a typical neutron star is huge. If an object were to fall from a height of one meter on a neutron star 12 kilometers in radius, it would reach the ground at around 1400 kilometers per second.^[45] However, even before impact, the tidal force would cause spaghettification, breaking any sort of an ordinary object into a stream of material.

Because of the enormous gravity, time dilation between a neutron star and Earth is significant. For example, eight years could pass on the surface of a neutron star, yet ten years would have passed on Earth, not including the time-dilation effect of the star's very rapid rotation.^[46]

Neutron star relativistic equations of state describe the relation of radius vs. mass for various models.^[47] The most likely radii for a given neutron star mass are bracketed by models AP4 (smallest radius) and MS2 (largest radius). E_B is the ratio of gravitational binding energy mass equivalent to the observed neutron star gravitational mass of M kilograms with radius R meters,^[48]

$${\displaystyle E_{\text{B}}={\frac {0.60\,\beta }{1-{\frac {\beta }{2}}}}}$$

$${\displaystyle \beta \ =G\,M/R\,{c}^{2}}$$

• ${\displaystyle G=6.67408\times 10^{-11}\,{\text{m}}^{3}{\text{kg}}^{-1}{\text{s}}^{-2}}$^[49]
• ${\displaystyle c=2.99792458\times 10^{8}\,{\text{m}}/{\text{s}}}$^[49]
• ${\displaystyle M_{\odot }=1.98855\times 10^{30}\,{\text{kg}}}$

and star masses "M" commonly reported as multiples of one solar mass,

$${\displaystyle M_{x}={\frac {M}{M_{\odot }}}}$$

$${\displaystyle E_{\text{B}}={\frac {886.0\,M_{x}}{R_{\left[{\text{in meters}}\right]}-738.3\,M_{x}}}}$$

A 2 M_☉ neutron star would not be more compact than 10,970 meters radius (AP4 model). Its mass fraction gravitational binding energy would then be 0.187, −18.7% (exothermic). This is not near 0.6/2 = 0.3, −30%.

The

Current understanding of the structure of neutron stars is defined by existing mathematical models, but it might be possible to infer some details through studies of

Current models indicate that matter at the surface of a neutron star is composed of ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps between them. It is possible that the nuclei at the surface are iron, due to iron's high binding energy per nucleon.^[51] It is also possible that heavy elements, such as iron, simply sink beneath the surface, leaving only light nuclei like helium and hydrogen.^[51] If the surface temperature exceeds 10⁶ kelvins (as in the case of a young pulsar), the surface should be fluid instead of the solid phase that might exist in cooler neutron stars (temperature <10⁶ kelvins).^[51]

The "atmosphere" of a neutron star is hypothesized to be at most several micrometers thick, and its dynamics are fully controlled by the neutron star's magnetic field. Below the atmosphere one encounters a solid "crust". This crust is extremely hard and very smooth (with maximum surface irregularities on the order of millimeters or less), due to the extreme gravitational field.^[52][53]

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. As this process continues at increasing depths, the

Neutron stars are detected from their electromagnetic radiation. Neutron stars are usually observed to pulse radio waves and other electromagnetic radiation, and neutron stars observed with pulses are called pulsars.

Pulsars' radiation is thought to be caused by particle acceleration near their

The radiation emanating from the magnetic poles of neutron stars can be described as magnetospheric radiation, in reference to the magnetosphere of the neutron star.^[56] It is not to be confused with magnetic dipole radiation, which is emitted because the magnetic axis is not aligned with the rotational axis, with a radiation frequency the same as the neutron star's rotational frequency.^[55]

If the axis of rotation of the neutron star is different from the magnetic axis, external viewers will only see these beams of radiation whenever the magnetic axis point towards them during the neutron star rotation. Therefore, periodic pulses are observed, at the same rate as the rotation of the neutron star.

In May 2022, astronomers reported an ultra-long-period radio-emitting neutron star

Over time, neutron stars slow, as their rotating magnetic fields in effect radiate energy associated with the rotation; older neutron stars may take several seconds for each revolution. This is called spin down. The rate at which a neutron star slows its rotation is usually constant and very small.

The

rotational period

, the time for one rotation of a neutron star. The spin-down rate, the rate of slowing of rotation, is then given the symbol ${\displaystyle {\dot {P}}}$ (P-dot), the

The spin-down rate (P-dot) of neutron stars usually falls within the range of 10⁻²² to 10⁻⁹ s⋅s⁻¹, with the shorter period (or faster rotating) observable neutron stars usually having smaller P-dot. As a neutron star ages, its rotation slows (as P increases); eventually, the rate of rotation will become too slow to power the radio-emission mechanism, and the neutron star can no longer be detected.^[55]

P and P-dot allow minimum magnetic fields of neutron stars to be estimated.^[55] P and P-dot can be also used to calculate the characteristic age of a pulsar, but gives an estimate which is somewhat larger than the true age when it is applied to young pulsars.^[55]

P and P-dot can also be combined with neutron star's moment of inertia to estimate a quantity called spin-down luminosity, which is given the symbol ${\displaystyle {\dot {E}}}$ (E-dot). It is not the measured luminosity, but rather the calculated loss rate of rotational energy that would manifest itself as radiation. For neutron stars where the spin-down luminosity is comparable to the actual

P and P-dot can also be plotted for neutron stars to create a P–P-dot diagram. It encodes a tremendous amount of information about the pulsar population and its properties, and has been likened to the Hertzsprung–Russell diagram in its importance for neutron stars.^[55]

Spin up

Neutron star rotational speeds can increase, a process known as spin up. Sometimes neutron stars absorb orbiting matter from companion stars, increasing the rotation rate and reshaping the neutron star into an

The most rapidly rotating neutron star currently known,

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 theoretical superfluid core of the neutron star from one metastable energy state to a lower one, thereby releasing energy that appears as an increase in the rotation rate.[67]^[66]

Anti-glitches

An anti-glitch, a sudden small decrease in rotational speed, or spin down, of a neutron star has also been reported.^[68] It occurred in the magnetar 1E 2259+586, that in one case produced an X-ray luminosity increase of a factor of 20, and a significant spin-down rate change. Current neutron star models do not predict this behavior. If the cause were internal this suggests differential rotation of the solid outer crust and the superfluid component of the magnetar's inner structure.^[68][66]

Population and distances

At present, there are about 3,200 known neutron stars in the Milky Way and the Magellanic Clouds, the majority of which have been detected as radio pulsars. Neutron stars are mostly concentrated along the disk of the Milky Way, although the spread perpendicular to the disk is large because the supernova explosion process can impart high translational speeds (400 km/s) to the newly formed neutron star.

Some of the closest known neutron stars are RX J1856.5−3754, which is about 400 light-years from Earth, and PSR J0108−1431 about 424 light years.^[69] RX J1856.5-3754 is a member of a close group of neutron stars called The Magnificent Seven. Another nearby neutron star that was detected transiting the backdrop of the constellation Ursa Minor has been nicknamed Calvera by its Canadian and American discoverers, after the villain in the 1960 film The Magnificent Seven. This rapidly moving object was discovered using the ROSAT Bright Source Catalog.

Neutron stars are only detectable with modern technology during the earliest stages of their lives (almost always less than 1 million years) and are vastly outnumbered by older neutron stars that would only be detectable through their blackbody radiation and gravitational effects on other stars.

Binary neutron star systems

About 5% of all known neutron stars are members of a

Binary systems containing neutron stars often emit X-rays, which are emitted by hot gas as it falls towards the surface of the neutron star. The source of the gas is the companion star, the outer layers of which can be stripped off by the gravitational force of the neutron star if the two stars are sufficiently close. As the neutron star accretes this gas, its mass can increase; if enough mass is accreted, the neutron star may collapse into a black hole.^[74]

Neutron star binary mergers and nucleosynthesis

The distance between two neutron stars in a close binary system is observed to shrink as

Neutron stars can host

At the meeting of the

In 1965, Antony Hewish and Samuel Okoye discovered "an unusual source of high radio brightness temperature in the Crab Nebula".^[87] This source turned out to be the Crab Pulsar that resulted from the great supernova of 1054.

In 1967, Iosif Shklovsky examined the X-ray and optical observations of Scorpius X-1 and correctly concluded that the radiation comes from a neutron star at the stage of accretion.^[88]

In 1967, Jocelyn Bell Burnell and Antony Hewish discovered regular radio pulses from PSR B1919+21. This pulsar was later interpreted as an isolated, rotating neutron star. The energy source of the pulsar is the rotational energy of the neutron star. The majority of known neutron stars (about 2000, as of 2010) have been discovered as pulsars, emitting regular radio pulses.

In 1968, Richard V. E. Lovelace and collaborators discovered period ${\displaystyle P\!\approx 33}$ ms of the

In 1971,

In 2003, Marta Burgay and colleagues discovered the first double neutron star system where both components are detectable as pulsars, PSR J0737−3039.^[96] The discovery of this system allows a total of 5 different tests of general relativity, some of these with unprecedented precision.

In 2010, Paul Demorest and colleagues measured the mass of the millisecond pulsar

In 2013, John Antoniadis and colleagues measured the mass of PSR J0348+0432 to be 2.01±0.04 M_☉, using white dwarf spectroscopy.^[98] This confirmed the existence of such massive stars using a different method. Furthermore, this allowed, for the first time, a test of general relativity using such a massive neutron star.

In August 2017, LIGO and Virgo made first detection of gravitational waves produced by colliding neutron stars (GW170817),^[99] leading to further discoveries about neutron stars.

In October 2018, astronomers reported that

A 2020 study by University of Southampton PhD student Fabian Gittins suggested that surface irregularities ("mountains") may only be fractions of a millimeter tall (about 0.000003% of the neutron star's diameter), hundreds of times smaller than previously predicted, a result bearing implications for the non-detection of gravitational waves from spinning neutron stars.^{[53][107][108]}

Using the

There are a number of types of object that consist of or contain a neutron star:

• Isolated neutron star (INS):^{[56][59][110][111]} not in a binary system.
  • Rotation-powered pulsar (RPP or "radio pulsar"):^[59]
    neutron stars that emit directed pulses of radiation towards us at regular intervals (due to their strong magnetic fields).
    • Rotating radio transient (RRATs):^[59] are thought to be pulsars which emit more sporadically and/or with higher pulse-to-pulse variability than the bulk of the known pulsars.
  • 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).
    • Soft gamma repeater (SGR).^[56]
    • Anomalous X-ray pulsar (AXP).^[56]
  • Radio-quiet neutron stars.
    • X-ray dim isolated neutron stars.^[59]
    • Central compact objects in supernova remnants (CCOs in SNRs): young, radio-quiet non-pulsating X-ray sources, thought to be Isolated Neutron Stars surrounded by supernova remnants.^[59]
• X-ray binaries
  .
  • Low-mass X-ray binary pulsars: a class of
    low-mass X-ray binaries
    (LMXB), a pulsar with a main sequence star, white dwarf or red giant.
    • Millisecond pulsar (MSP) ("recycled pulsar").
      • "Spider Pulsar", a pulsar where their companion is a semi-degenerate star.^[112]
        • "Black Widow" pulsar, a pulsar that falls under the "Spider Pulsar" if the companion has extremely low mass (less than 0.1 M_☉).
        • "Redback" pulsar, are if the companion is more massive.
      • Sub-millisecond pulsar.^[113]
    • 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.
  • Intermediate-mass X-ray binary pulsars: a class of
    intermediate-mass X-ray binaries
    (IMXB), a pulsar with an intermediate mass star.
  • High-mass X-ray binary pulsars: a class of
    high-mass X-ray binaries
    (HMXB), a pulsar with a massive star.
  • Binary pulsars: a pulsar with a binary companion, often a white dwarf or neutron star.
  • X-ray tertiary (theorized).^[114]

There are also a number of theorized compact stars with similar properties that are not actually neutron stars.

• Protoneutron star (PNS), theorized^[115]
• Exotic star
  • Thorne–Żytkow object: currently a hypothetical merger of a neutron star into a red giant star.
  • quark matter, or strange matter
    . As of 2018, there are three candidates.
  • Electroweak star: currently a hypothetical type of extremely heavy neutron star, in which the quarks are converted to leptons through the electroweak force, but the gravitational collapse of the neutron star is prevented by radiation pressure. As of 2018, there is no evidence for their existence.
  • preon matter. As of 2018, there is no evidence for the existence of preons
    .

• Black Widow Pulsar – a millisecond pulsar that is very massive
• PSR J0952-0607 – the heaviest neutron star with 2.35+0.17
  −0.17 M_☉, a type of Black Widow Pulsar^[8][116]
• LGM-1 (now known as PSR B1919+21) – the first recognized radio-pulsar. It was discovered by Jocelyn Bell Burnell
  in 1967.
• PSR B1257+12 (Also known as Lich) – the first neutron star discovered with planets (a millisecond pulsar).
• PSR B1509−58 – source of the "Hand of God" photo shot by the Chandra X-ray Observatory
• RX J1856.5−3754 – the closest neutron star
• The Magnificent Seven – a group of nearby, X-ray dim isolated neutron stars
• PSR J0348+0432 – the most massive neutron star with a well-constrained mass, 2.01±0.04 M_☉
• SWIFT J1756.9-2508
  – a millisecond pulsar with a stellar-type companion with planetary range mass (below brown dwarf)
• Swift J1818.0-1607
  – the youngest-known magnetar

Gallery

• Neutron stars containing 500,000 Earth-masses in 25-kilometer-diameter (16 mi) sphere
• Neutron stars colliding
• Neutron star collision
• 
  Artist's impression of a neutron star bending light

See also

Notes

References

1. S2CID 59065632
   .
2. ISBN 978-1-4684-0491-3. Archived
   from the original on 2017-01-31. Retrieved 2016-03-21.
3. ISBN 978-0-495-56203-0. Archived
   from the original on 2021-02-06. Retrieved 2018-02-22.
4. doi:10.1103/PhysRev.55.364. Archived
   (PDF) from the original on 2018-07-22. Retrieved 2019-06-30.
5. doi:10.1103/PhysRev.55.374
   .
6. ^ "Neutron Stars" (PDF). www.astro.princeton.edu. Archived (PDF) from the original on 9 September 2021. Retrieved 14 December 2018.
7. S2CID 17516814
   .
8. ^ ^{a b} Croswell, Ken (2022-07-22). "The heaviest neutron star on record is 2.35 times the mass of the sun". Science News. Retrieved 2022-07-25.
9. ^ "Q&A: Supernova Remnants and Neutron Stars", Chandra.harvard.edu (September 5, 2008)
10. ^ "Magnetic Hydrogen Atmosphere Models and the Neutron Star RX J1856.5−3754" (PDF), Wynn C. G. Ho et al., Monthly Notices of the Royal Astronomical Society, 375, pp. 821-830 (2007), submitted December 6, 2006, ArXiv:astro-ph/0612145. The authors calculated what they considered to be "a more realistic model, which accounts for magnetic field and temperature variations over the neutron star surface as well as general relativistic effects," which yielded an average surface temperature of 4.34+0.02
    −0.06×10⁵ K at a confidence level of 2𝜎 (95%); see §4, Fig. 6 in their paper for details.
11. ^ "The Sun is less active than other solar-like stars" (PDF), Timo Reinhold et al., ArXiv:astro-ph.SR (May 4, 2020) ArXiv:2005.01401
12. ^ "Tour the ASM Sky". heasarc.gsfc.nasa.gov. Archived from the original on 2021-10-01. Retrieved 2016-05-23.
13. ^ "Density of the Earth". 2009-03-10. Archived from the original on 2013-11-12. Retrieved 2016-05-23.
14. S2CID 14945340
    .
15. ^ Naeye, Robert (2006-01-13). "Spinning Pulsar Smashes Record". Sky & Telescope. Archived from the original on 2007-12-29. Retrieved 2008-01-18.
16. ^ "NASA.gov". Archived from the original on 2018-09-08. Retrieved 2020-08-05.
17. ISBN 978-3-540-49912-1. Archived
    from the original on 29 April 2021. Retrieved 6 September 2017.
18. S2CID 217162243
    .
19. Bibcode:1996A&A...305..871B
    .
20. ISBN 978-0-521-80105-8. Archived
    from the original on 2017-01-31. Retrieved 2016-06-30.
21. ^
    ISBN 978-0-387-33543-8
    .
22. ^ ^{a b} "The Remarkable Properties of Neutron Stars - Fresh Chandra News". ChandraBlog. 2013-03-28. Retrieved 2022-05-16.
23. doi:10.1093/mnras/sty2460
    .
24. S2CID 119120778
    .
25. S2CID 52026378
    .
26. S2CID 119359694
    .
27. S2CID 118647384
    .
28. ^ "Black holes". Goddard Space Flight Center (GSFC). National Aeronautics and Space Administration (NASA). Archived from the original on 2014-10-29. Retrieved 2010-06-23.
29. ^
    doi:10.1063/1.4909560
    .
30. S2CID 6247160
    .
31. ^ "Calculating a Neutron Star's Density". Archived from the original on 2006-02-24. Retrieved 2006-03-11. NB 3×10¹⁷ kg/m³ is 3×10¹⁴ g/cm³
32. S2CID 119226325
    .
33. ^ "quantum wave-particle duality: Topics by Science.gov". www.science.gov. Retrieved 2023-06-10.
34. PMID 30524193
    .
35. S2CID 14819350
    .
36. ISSN 0066-4243
    .
37. ^
    arXiv:astro-ph/0307133
    .
38. ^ "McGill SGR/AXP Online Catalog". Archived from the original on 23 July 2020. Retrieved 2 Jan 2014.
39. ^
    PMID 12561456
    .
40. S2CID 15906305
    .
41. ^ "Eric Weisstein's World of Physics". scienceworld.wolfram.com. Archived from the original on 2019-04-23.
42. ^ Duncan, Robert C. (March 2003). "'Magnetars', soft gamma repeaters & very strong magnetic fields". Archived from the original on 2020-01-19. Retrieved 2018-04-17.
43. ^ ^{a b c} Zahn, Corvin (1990-10-09). "Tempolimit Lichtgeschwindigkeit" (in German). Archived from the original on 2021-01-26. Retrieved 2009-10-09. Durch die gravitative Lichtablenkung ist mehr als die Hälfte der Oberfläche sichtbar. Masse des Neutronensterns: 1, Radius des Neutronensterns: 4, ... dimensionslosen Einheiten (c, G = 1)
44. ISBN 978-0-521-54622-5. Archived
    from the original on 2017-01-31. Retrieved 2016-06-09.
45. ^ "Peligroso lugar para jugar tenis". Datos Freak (in Spanish). Archived from the original on 11 June 2016. Retrieved 3 June 2016.
46. ISBN 978-0-300-21363-8
    .
47. ^ Neutron Star Masses and Radii Archived 2011-12-17 at the Wayback Machine, p. 9/20, bottom
48. S2CID 14782250
    .
49. ^ ^{a b} CODATA 2014
50. ^ ^{a b} NASA. Neutron Star Equation of State Science Retrieved 2011-09-26
51. ^
    S2CID 250831196
    .
52. ^ Darling, David. "neutron star". www.daviddarling.info. Archived from the original on 2009-01-24. Retrieved 2009-01-12.
53. ^ ^{a b} Baker, Harry (21 July 2021). "Neutron star 'mountains' are actually microscopic bumps less than a millimeter tall". Live Science. Archived from the original on 25 July 2021. Retrieved 25 July 2021.
54. S2CID 119253979
    .
55. ^ ^{a b c d e f g h i j k} Condon, J. J. & Ransom, S. M. "Pulsar Properties (Essential radio Astronomy)". National Radio Astronomy Observatory. Archived from the original on 10 April 2016. Retrieved 24 March 2016.
56. ^ ^{a b c d e f} Pavlov, George. "X-ray Properties of Rotation Powered Pulsars and Thermally Emitting Neutron Stars" (PDF). pulsarastronomy.net. Archived (PDF) from the original on 6 December 2015. Retrieved 6 April 2016.
57. S2CID 249212424
    .
58. ^ "Unusual neutron star discovered in stellar graveyard". The University of Sydney. Retrieved 2022-06-01.
59. ^
    S2CID 118470472
    .
60. S2CID 119184617
    .
61. ^ ^{a b} "7. Pulsars at Other Wavelengths". Frontiers of Modern Astronomy. Jodrell Bank Centre for Astrophysics. Archived from the original on 10 April 2016. Retrieved 6 April 2016.
62. S2CID 6777734
    .
63. ^ Zhang, B. "Spin-Down Power of Magnetars" (PDF). Universidade Federal do Rio Grande do Sul. Archived (PDF) from the original on 6 February 2021. Retrieved 24 March 2016.
64. S2CID 14945340
    .
65. S2CID 119405361
    .
66. ^
    ISBN 978-981-12-2093-7
67. ^ Alpar, M. Ali (1 January 1998). "Pulsars, glitches and superfluids". Physicsworld.com. Archived from the original on 6 December 2008. Retrieved 12 January 2009.
68. ^
    S2CID 4382559
    .
69. S2CID 10639250
    .
70. Bibcode:2006csxs.book..623T
    . Fig. 16.4. Illustration of the relative distribution of all ~ 1500 radio pulsars observed. About 4% are members of a binary system.
71. S2CID 119471204
    .
72. PMID 29099225
    .
73. PMID 26918975
    .
74. Bibcode:2010csxs.book.....L
    .
75. doi:10.1086/159690
    .
76. S2CID 205235329
    .
77. Science. Archived
    from the original on 18 October 2017. Retrieved 16 October 2017.
78. ^ Overbye, Dennis (16 October 2017). "LIGO Detects Fierce Collision of Neutron Stars for the First Time". The New York Times. Archived from the original on 16 October 2017. Retrieved 16 October 2017.
79. doi:10.1038/nature.2017.22482
    .
80. S2CID 217163611
    .
81. ^ Urry, Meg (July 20, 2013). "Gold comes from stars". CNN. Archived from the original on July 22, 2017. Retrieved July 20, 2013.
82. ^ "Gemini Telescopes Help Uncover Origins of Castaway Gamma-Ray Bursts". Retrieved 16 December 2022.
83. doi:10.1103/PhysRev.46.76.2. Archived
    (PDF) from the original on 2021-02-24. Retrieved 2019-09-16.
84. ^ Landau, Lev D. (1932). "On the theory of stars". Phys. Z. Sowjetunion. 1: 285–288.
85. ISBN 978-0387335438
    .
86. S2CID 4076465
    .
87. S2CID 123416790
    .
88. doi:10.1086/180001
    .
89. S2CID 4213758
    .
90. S2CID 4294389
    .
91. Bibcode:2012Obs...132..186L
    .
92. ISBN 978-981-02-4744-7. Archived
    from the original on 2021-02-06. Retrieved 2016-11-29.
93. ISBN 978-0-387-33367-0. Archived
    from the original on 2021-02-06. Retrieved 2016-11-29.
94. ISBN 978-0-387-47301-7. Archived
    from the original on 2021-02-06. Retrieved 2016-11-29.
95. ISBN 978-0-521-83954-9. Archived
    from the original on 2021-02-06. Retrieved 2016-11-29.
96. ISBN 978-981-02-4744-7. Archived
    from the original on 2021-02-06. Retrieved 2016-11-29.
97. S2CID 205222609
    .
98. S2CID 15221098
    .
99. ^ Burtnyk, Kimberly M. (16 October 2017). "LIGO Detection of Colliding Neutron Stars Spawns Global Effort to Study the Rare Event". Archived from the original on 23 October 2017. Retrieved 17 November 2017.
100. EurekAlert!. Archived
     from the original on 16 October 2018. Retrieved 17 October 2018.
101. PMID 30327476
     .
102. ^ Mohon, Lee (16 October 2018). "GRB 150101B: A Distant Cousin to GW170817". NASA. Archived from the original on 22 March 2019. Retrieved 17 October 2018.
103. ^ Wall, Mike (17 October 2018). "Powerful Cosmic Flash Is Likely Another Neutron-Star Merger". Space.com. Archived from the original on 17 October 2018. Retrieved 17 October 2018.
104. EurekAlert!. Archived
     from the original on 8 July 2019. Retrieved 8 July 2019.
105. ^ Finley, Dave (8 July 2019). "New Method May Resolve Difficulty in Measuring Universe's Expansion". National Radio Astronomy Observatory. Archived from the original on 8 July 2019. Retrieved 8 July 2019.
106. S2CID 119547153
     .
107. ^ Plait, Phil (23 July 2021). "The tallest mountain on a neutron star may be a fraction of a millimeter tall". Syfy. Archived from the original on 25 July 2021. Retrieved 25 July 2021.
108. doi:10.1093/mnras/stab2048
     .
109. Wikidata Q124719867
     .
110. S2CID 117102095
     .
111. Bibcode:2000IAUS..195..103P
     .
112. S2CID 201646167
     .
113. doi:10.1143/PTP.81.1006
     .
114. doi:10.1093/mnras/stz2572
     .
115. S2CID 117093903
     .
116. S2CID 250451299
     .

Sources

• "The following points are made by R.N. Manchester (Science 2004 304:542)". scienceweek.com. Astrophysics: On observed pulsars. 2004. Archived from the original on 14 July 2007. Retrieved 6 August 2004.
• Glendenning, Norman K.; Kippenhahn, R.; Appenzeller, I.; Borner, G.; Harwit, M. (2000). Compact Stars (2nd ed.).
• Kaaret, P.; Prieskorn, Z.; in 't Zand, J.J.M.; Brandt, S.; Lund, N.; Mereghetti, S.; et al. (2006). "Evidence for 1122 Hz X-ray burst oscillations from the neutron-star X-ray transient XTE J1739-285". The Astrophysical Journal. 657 (2): L97.
  S2CID 119405361
  .

External links

Wikimedia Commons has media related to Neutron stars.

• Hessels, Jason W. T; Ransom, Scott M; Stairs, Ingrid H; Freire, Paulo C. C; Kaspi, Victoria M; Camilo, Fernando (2003). "Neutron Stars for Undergraduates". American Journal of Physics. 72 (2004): 892–905.
  S2CID 27807404
  .
  • Silbar, Richard R; Reddy, Sanjay (2005). "Erratum: "Neutron stars for undergraduates" [Am. J. Phys. 72 (7), 892–905 (2004)]". American Journal of Physics. 73 (3): 286.
    doi:10.1119/1.1852544
    .
• NASA on pulsars
• "NASA Sees Hidden Structure Of Neutron Star In Starquake". SpaceDaily.com. April 26, 2006
• "Mysterious X-ray sources may be lone neutron stars" David Shiga. New Scientist. 23 June 2006
• "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.