Editing Neutron star (section)

==Radiation==
[[File:Pulsar anim.ogv|thumb|Animation of a rotating pulsar. The sphere in the middle represents the neutron star, the curves indicate the magnetic field lines and the protruding cones represent the emission zones.]]

===Pulsars===
{{Main|Pulsar}}

Neutron stars are detected from their [[electromagnetic radiation]]. Neutron stars are usually observed to [[Pulse (physics)|pulse]] [[radio wave]]s 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 [[Poles of astronomical bodies#Magnetic poles|magnetic poles]], which need not be aligned with the [[axis of rotation|rotational axis]] of the neutron star. It is thought that a large [[electrostatic field]] builds up near the magnetic poles, leading to [[electron emission]].<ref name="nrao" /> These electrons are magnetically accelerated along the field lines, leading to [[curvature radiation]], with the radiation being strongly [[Polarization (waves)|polarized]] towards the plane of curvature.<ref name="nrao" /> In addition, high-energy [[photons]] can interact with lower-energy photons and the magnetic field for [[electron−positron pair production]], which through [[electron–positron annihilation]] leads to further high-energy photons.<ref name="nrao" />

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.<ref name="pavlov" /> It is not to be confused with ''[[Multipole radiation|magnetic dipole radiation]]'', which is emitted because the [[poles of astronomical bodies#Magnetic poles|magnetic]] [[Rotation around a fixed axis|axis]] is not aligned with the rotational axis, with a radiation frequency the same as the neutron star's rotational frequency.<ref name="nrao" />

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 function|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 [[PSR J0901-4046]], with spin properties distinct from the known neutron stars.<ref>{{Cite journal |last1=Caleb |first1=Manisha|author1-link=Manisha Caleb |last2=Heywood |first2=Ian |last3=Rajwade |first3=Kaustubh |last4=Malenta |first4=Mateusz |last5=Willem Stappers |first5=Benjamin |last6=Barr |first6=Ewan |last7=Chen |first7=Weiwei |last8=Morello |first8=Vincent |last9=Sanidas |first9=Sotiris |last10=van den Eijnden |first10=Jakob |last11=Kramer |first11=Michael |date=2022-05-30 |title=Discovery of a radio-emitting neutron star with an ultra-long spin period of 76 s |journal=Nature Astronomy |volume=6 |issue=7 |language=en |pages=828–836 |doi=10.1038/s41550-022-01688-x |pmid=35880202 |pmc=7613111 |arxiv=2206.01346 |bibcode=2022NatAs...6..828C |s2cid=249212424 |issn=2397-3366}}</ref> It is unclear how its radio emission is generated, and it challenges the current understanding of how pulsars evolve.<ref>{{Cite web |title=Unusual neutron star discovered in stellar graveyard |url=https://www.sydney.edu.au/news-opinion/news/2022/05/31/unusual-neutron-star-discovered-in-stellar-graveyard.html |access-date=2022-06-01 |website=The University of Sydney |language=en-AU}}</ref>

===Non-pulsating neutron stars===
In addition to pulsars, non-pulsating neutron stars have also been identified, although they may have minor periodic variation in luminosity.<ref name="cco"/><ref name="non-pulsating">{{cite journal |title=A non-pulsating neutron star in the supernova remnant HESS J1731-347 / G353.6–0.7 with a carbon atmosphere |first1=D. |last1=Klochkov |first2=G. |last2=Puehlhofer |first3=V. |last3=Suleimanov |first4=S. |last4=Simon |first5=K. |last5=Werner |first6=A. |last6=Santangelo |journal=Astronomy & Astrophysics |volume=556 |pages=A41 |year=2013 |doi=10.1051/0004-6361/201321740 |arxiv=1307.1230 |bibcode=2013A&A...556A..41K |s2cid=119184617 }}</ref> This seems to be a characteristic of the X-ray sources known as [[Central Compact Object]]s in [[supernova remnant]]s (CCOs in SNRs), which are thought to be young, radio-quiet isolated neutron stars.<ref name="cco">{{Cite journal |arxiv=0712.2209 |year=2008 |first=Andrea |last=De Luca |volume=983 |pages=311–319 |doi=10.1063/1.2900173 |title=Central Compact Objects in Supernova Remnants |journal=AIP Conference Proceedings |citeseerx=10.1.1.769.699 |bibcode=2008AIPC..983..311D |s2cid=118470472 }}</ref>

===Spectra===
In addition to [[radio wave|radio]] emissions, neutron stars have also been identified in other parts of the [[electromagnetic spectrum]]. This includes [[Light|visible light]], [[near infrared]], [[ultraviolet]], [[X-ray]]s, and [[gamma ray]]s.<ref name="pavlov">{{cite web |url=http://www.pulsarastronomy.net/IAUS291/download/Oral/IAUS291_PavlovG.pdf |title=X-ray Properties of Rotation Powered Pulsars and Thermally Emitting Neutron Stars |publisher=pulsarastronomy.net |access-date=6 April 2016 |first=George |last=Pavlov |archive-date=6 December 2015 |archive-url=https://web.archive.org/web/20151206215220/http://www.pulsarastronomy.net/IAUS291/download/Oral/IAUS291_PavlovG.pdf |url-status=live }}</ref> Pulsars observed in X-rays are known as [[Accretion-powered pulsars|X-ray pulsars if accretion-powered]], while those identified in visible light are known as [[optical pulsar]]s. The majority of neutron stars detected, including those identified in optical, X-ray, and gamma rays, also emit radio waves;<ref name="jb">{{cite web |url=http://www.jb.man.ac.uk/distance/frontiers/pulsars/section7.html |title=7. Pulsars at Other Wavelengths |publisher=Jodrell Bank Centre for Astrophysics |website=Frontiers of Modern Astronomy |access-date=6 April 2016 |archive-date=10 April 2016 |archive-url=https://web.archive.org/web/20160410062808/http://www.jb.man.ac.uk/distance/frontiers/pulsars/section7.html |url-status=live }}</ref> the [[Crab Pulsar]] produces electromagnetic emissions across the spectrum.<ref name="jb" /> However, there exist neutron stars called [[radio-quiet neutron star]]s, with no radio emissions detected.<ref name="ras">{{cite journal |title=The implications of radio-quiet neutron stars |first1=K. T. S. |last1=Brazier |first2=S. |last2=Johnston |name-list-style=amp |journal=Monthly Notices of the Royal Astronomical Society |volume=305 |issue=3 |pages=671 |date=August 2013 |doi=10.1046/j.1365-8711.1999.02490.x |doi-access=free |arxiv=astro-ph/9803176 |bibcode=1999MNRAS.305..671B |s2cid=6777734 }}</ref>