Schematic view of a pulsar. The sphere in the middle represents the neutron star, the curves indicate the magnetic field lines and the protruding cones represent the emission beams.

Composite Optical/X-ray image of the Crab Nebula, showing synchrotron emission in the surrounding pulsar wind nebula, powered by injection of magnetic fields and particles from the central pulsar.

Pulsars are highly magnetized rotating neutron stars which emit a beam of detectable electromagnetic radiation in the form of radio waves. Their observed periods range from 1.5 ms to 8.5 s.^[1] The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects, the rotation period and thus the interval between observed pulses are very regular. For some pulsars, the regularity of pulsation is as precise as an atomic clock.^[2] Pulsars are known to have planets orbiting them, as in the case of PSR B1257+12. Werner Becker of the Max-Planck-Institut für extraterrestrische Physik said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work."^[3] Pulsar can refer to A type of star. ... Image File history File links Download high-resolution version (2400x2400, 314 KB) A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. ... Image File history File links Download high-resolution version (2400x2400, 314 KB) A composite image of the Crab Nebula showing the X-ray (blue), and optical (red) images superimposed. ... The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. ... Synchrotron radiation is electromagnetic radiation, similar to cyclotron radiation, but generated by the acceleration of ultrarelativistic (i. ... A pulsar wind nebula (also known as a plerion, Greek for full) is a synchrotron nebula powered by the relativistic wind of an energetic pulsar. ... For the story by Larry Niven, see Neutron Star (story). ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... “Nuclear Clock” redirects here. ... PSR B1257+12 (sometimes abbreviated to PSR 1257+12) is a pulsar located 980 light years from Earth. ... The Max Planck Institute for Extraterrestrial Physics is a Max Planck Institute, located in Garching, near Munich, Germany. ...

History

Discovery

The first pulsar was observed in July 1968 by Jocelyn Bell Burnell and Antony Hewish. Initially baffled as to the seemingly unnatural regularity of its emissions, they dubbed their discovery LGM-1, for "little green men" (a comical name for intelligent beings of extraterrestrial origin). Their pulsar was later dubbed CP 1919, and is now known by a number of designators including PSR 1919+21, PSR B1919+21 and PSR J1921+2153. Dame Jocelyn Bell Burnell, DBE, FRS FRAS, Ph. ... Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for Physics in 1974 (together with fellow radio-astronomer Martin Ryle) for his work on the development of radio aperture synthesis and its role in the discovery of pulsars. ... For other uses, see Little Green Men (disambiguation). ... Green people redirects here. ... The first radio pulsar, CP 1919, with a pulse period of 1. ...

According to Martin Rees^{[citation needed]}, the hypothesis that pulsars were beacons from extraterrestrial civilizations was never taken very seriously. However, astrophysicist Peter A. Sturrock writes that the possibility of an extraterrestrial origin was "seriously considered ... They debated this possibility and decided that, if this proved to be correct, they could not make an announcement without checking with higher authorities. There was even some discussion about whether it might be in the best interests of mankind to destroy the evidence and forget it!" (Sturrock, 154) The Right Honourable Martin John Rees, Baron Rees of Ludlow, FRS (born 23 June 1942) is a professor of astronomy. ... Peter Andrew Sturrock (born 1924) is an British scientist. ...

Although CP 1919 emits in radio wavelengths, pulsars have, subsequently, been found to emit in the X-ray and/or gamma ray wavelengths. Radio waves are electromagnetic waves occurring on the radio frequency portion of the electromagnetic spectrum. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ...

The word pulsar is a contraction of "pulsating star", and first appeared in print in 1968:

The suggestion that pulsars were rotating neutron stars was put forth independently by Thomas Gold and Franco Pacini in 1968, and was soon proven beyond doubt by the discovery of a pulsar with a very short (33-millisecond) pulse period in the Crab nebula. This article is about Thomas Gold, an Austrian astrophysicist. ... Year 1968 (MCMLXVIII) was a leap year starting on Monday (link will display full calendar) of the Gregorian calendar. ... One millisecond is one-thousandth of a second. ... The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. ...

In 1974, Antony Hewish became the first astronomer to be awarded the Nobel Prize in physics. Considerable controversy is associated with the fact that Professor Hewish was awarded the prize while Bell, who made the initial discovery while she was his Ph.D student, was not. Year 1974 (MCMLXXIV) was a common year starting on Tuesday (link will display full calendar) of the 1974 Gregorian calendar. ... Hannes Alfvén (1908–1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ...

The Vela Pulsar and its surrounding pulsar wind nebula.

Download high resolution version (600x630, 51 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (600x630, 51 KB) Wikipedia does not have an article with this exact name. ... The Vela Pulsar is a radio, optical, X-ray and gamma-emitting pulsar associated with Vela Supernova Remnant, in the constellation of Vela. ... A pulsar wind nebula (also known as a plerion, Greek for full) is a synchrotron nebula powered by the relativistic wind of an energetic pulsar. ...

Subsequent history

In 1974, Joseph Hooton Taylor, Jr. and Russell Hulse discovered, for the first time, a pulsar in a binary system, PSR B1913+16. This pulsar orbits another neutron star with an orbital period of just eight hours. Einstein's theory of general relativity predicts that this system should emit strong gravitational radiation, causing the orbit to continually contract as it loses orbital energy. Observations of the pulsar soon confirmed this prediction, providing the first ever evidence of the existence of gravitational waves. As of 2004, observations of this pulsar continue to agree with general relativity. In 1993, the Nobel prize in physics was awarded to Taylor and Hulse for the discovery of this pulsar. Year 1974 (MCMLXXIV) was a common year starting on Tuesday (link will display full calendar) of the 1974 Gregorian calendar. ... Joseph H. Taylor, Jr. ... Russell Alan Hulse (born November 28, 1950) is an American physicist and winner of the Nobel Prize in Physics, shared with his thesis advisor Joseph Hooton Taylor Jr. ... For the band, see Binary Star (band). ... PSR B1913+16 is a pulsar in a binary star system, in orbit with another star around a common center of mass. ... “Einstein” redirects here. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In astrodynamics the specific orbital energy (or vis-viva energy) of an orbiting body traveling through space under standard assumptions is the sum of its potential energy () and kinetic energy () per unit mass. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Year 1993 (MCMXCIII) was a common year starting on Friday (link will display full 1993 Gregorian calendar). ...

In 1982, a pulsar with a rotation period of just 1.6 milliseconds was discovered, by Shri Kulkarni and Don Backer. Observations soon revealed that its magnetic field was much weaker than ordinary pulsars, while further discoveries cemented the idea that a new class of object, the "millisecond pulsars" (MSPs) had been found. MSPs are believed to be the end product of X-ray binaries. Owing to their extraordinarily rapid and stable rotation, MSPs can be used by astronomers as clocks rivalling the stability of the best atomic clocks on Earth. Factors affecting the arrival time of pulses at the Earth by more than a few hundred nanoseconds can be easily detected and used to make precise measurements. Physical parameters accessible through pulsar timing include the 3D position of the pulsar, its proper motion, the electron content of the interstellar medium along the propagation path, the orbital parameters of any binary companion, the pulsar rotation period and its evolution with time. (These are computed from the raw timing data by Tempo, a computer program specialized for this task.) After these factors have been taken into account, deviations between the observed arrival times and predictions made using these parameters can be found and attributed to one of three possibilities: intrinsic variations in the spin period of the pulsar, errors in the realization of Terrestrial Time against which arrival times were measured, or the presence of background gravitational waves. Scientists are currently attempting to resolve these possibilities by comparing the deviations seen amongst several different pulsars, forming what is known as a Pulsar Timing Array. With luck, these efforts may lead to a time scale a factor of ten or better than currently available, and the first ever direct detection of gravitational waves. Year 1982 (MCMLXXXII) was a common year starting on Friday (link displays the 1982 Gregorian calendar). ... 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. ... X-ray binaries are a class of binary stars that are very luminous in X-rays. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ... An atomic clock is a type of clock that uses an atomic resonance frequency standard as its counter. ... To help compare orders of magnitude of different times this page lists times between 10−9 seconds and 10−8 seconds (1 nanosecond and 10 nanoseconds) See also times of other orders of magnitude. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... For other uses, see Electron (disambiguation). ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... Terrestrial Time (TT) is the modern time standard for time on the surface of the Earth. ... A time scale specifies divisions (scale) of time. ...

The first ever extrasolar planets were found orbiting a MSP, by Aleksander Wolszczan. This discovery presented important evidence concerning the widespread existence of planets outside the solar system, although it is very unlikely that any life form could survive in the environment of intense radiation near a pulsar. Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ... Aleksander Wolszczan (b. ... This article is about the Solar System. ... Lifeform is the physical entity which encompasses a life. ...

Pulsar classes

Three distinct classes of pulsars are currently known to astronomers, according to the source of energy that powers the radiation: Galileo is often referred to as the Father of Modern Astronomy. ...

• Rotation-powered pulsars, where the loss of rotational energy of the star powers the radiation
• Accretion-powered pulsars (accounting for most but not all X-ray pulsars), where the gravitational potential energy of accreted matter is the energy source (producing X-rays that are observable from Earth), and
• Magnetars, where the decay of an extremely strong magnetic field powers the radiation.

Although all three classes of objects are neutron stars, their observable behaviour and the underlying physics are quite different. There are, however, connections. For example, X-ray pulsars are probably old rotation-powered pulsars that have already lost most of their energy, and have only become visible again after their binary companions expanded and began transferring matter on to the neutron star. The process of accretion can in turn transfer enough angular momentum to the neutron star to "recycle" it as a rotation-powered millisecond pulsar. It has been suggested that this article or section be merged into Pulsar. ... The rotational energy or angular kinetic energy is the kinetic energy due to the rotation of an object and is part of its total kinetic energy. ... An X-ray pulsar is a neutron star with a powerful magnetic field that gives rise to regular X_ray pulses. ... An X-ray pulsar is a neutron star with a powerful magnetic field that gives rise to regular X-ray pulses. ... Potential energy can be thought of as energy stored within a physical system. ... See also: Accretion (finance) Accretion is increase in size by gradual addition of smaller parts. ... Artists conception of a magnetar, with magnetic field lines 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 radiation, particularly X-rays and gamma-rays. ... For the indie-pop band, see The Magnetic Fields. ... An X-ray pulsar is a neutron star with a powerful magnetic field that gives rise to regular X-ray pulses. ... For the band, see Binary Star (band). ... This box:      This gyroscope remains upright while spinning due to its angular momentum. ... 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. ...

Naming

Initially pulsars were named with letters of the discovering observatory followed by their right ascension (e.g. CP 1919). As more pulsars were discovered, the letter code became unwieldy and so the convention was then superseded by the letters PSR (Pulsating Source of Radio) followed by the pulsar's right ascension and degrees of declination (e.g. PSR 0531+21) and sometimes declination to a tenth of a degree (e.g. PSR 1913+167). Pulsars that are very close together sometimes have letters appended (e.g. PSR 0021-72C and PSR 0021-72D).

The modern convention is to prefix the older numbers with a B (e.g. PSR B1919+21) with the B meaning the coordinates are for the 1950.0 epoch. All new pulsars have a J indicating 2000.0 coordinates and also have declination including minutes (e.g. PSR J1921+2153). Pulsars that were discovered before 1993 tend to retain their B names rather than use their J names (e.g. PSR J1921+2153 is more commonly known as PSR B1919+21). Recently discovered pulsars only have a J name (e.g. PSR J0437-4715). All pulsars have a J name that provides more precise coordinates of its location in the sky.^[5]

Glitch prediction

In June 2006, astronomer John Middleditch and his team at LANL announced the first prediction of glitches with observational data from the Rossi X-ray Timing Explorer. They used observations of the pulsar PSR J0537-6910. Los Alamos National Laboratory, aerial view from 1995. ... Glitch is a sudden increase in the rotational frequency of a rotation-powered pulsar. ... The Rossi X-ray Timing Explorer (RXTE) satellite observes the fast-moving, high-energy worlds of black holes, neutron stars, X-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. ... PSR J0537-6910 is a pulsar that is 4,000 years old (plus light travel time to Earth), and 170,000 light years away, in the southern sky. ...

Applications

The study of pulsars has resulted in many applications in physics and astronomy. Striking examples include the confirmation of the existence of gravitational radiation as predicted by general relativity and the first detection of an extrasolar planetary system. To meet Wikipedias quality standards, this article or section may require cleanup. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ...

As probes of the interstellar medium

The radiation from pulsars passes through the interstellar medium (ISM) before reaching Earth. Free electrons in the warm (8000 K), ionized component of the ISM and H II regions affect the radiation in two primary ways. The resulting changes to the pulsar's radiation provide an important probe of the ISM itself.^[6] The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... For other uses, see Electron (disambiguation). ... NGC 604, a giant H II region in the Triangulum Galaxy. ...

Due to the dispersive nature of the interstellar plasma, lower-frequency radio waves travel through the medium faster than higher-frequency radio waves. The resulting delay in the arrival of pulses at a range of frequencies is directly measurable as the dispersion measure of the pulsar. The dispersion measure is the total column density of free electrons between the observer and the pulsar, Dispersion of a light beam in a prism. ... Look up plasma in Wiktionary, the free dictionary. ...

where D is the distance from the pulsar to the observer and n_e is the electron density of the ISM. The dispersion measure is used to construct models of the free electron distribution in the Milky Way Galaxy.^[7] The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia Kuklos; or simply the Galaxy) is a barred spiral galaxy in the Local Group, and has special significance to humanity as the location of the solar system, which is located near the Orion...

Additionally, turbulence in the interstellar gas causes density inhomogeneities in the ISM which cause scattering of the radio waves from the pulsar. The resulting scintillation of the radio waves—the same effect as the twinkling of a star in visible light due to density variations in the Earth's atmosphere—can be used to reconstruct information about the small scale variations in the ISM.^[8] Due to the high velocity (up to several hundred km/sec) of many pulsars, a single pulsar scans the ISM rapidly, which results in changing scintillation patterns over timescales of a few minutes.^[9] In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic, stochastic property changes. ... Scattering is a general physical process whereby some forms of radiation, such as light, sound or moving particles, for example, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which it passes. ... Scintillation or twinkling are generic terms for rapid variations in apparent brightness or color of a distant luminous object viewed through the atmosphere. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...

Significant pulsars

• The first radio pulsar CP 1919 (now known as PSR 1919+21), with a pulse period of 1.337 seconds and a pulse width of 0.04 second, was discovered in 1967 (Nature 217:709-713, 1968).
• The first binary pulsar, PSR 1913+16, whose orbit is decaying at the exact rate predicted due to the emission of gravitational radiation by general relativity
• The first millisecond pulsar, PSR B1937+21
• The brightest millisecond pulsar, PSR J0437-4715
• The first X-ray pulsar, Cen X-3
• The first accreting millisecond X-ray pulsar, SAX J1808.4-3658
• The first extrasolar planets to be discovered orbit the pulsar PSR B1257+12
• The first double pulsar binary system, PSR J0737−3039
• The magnetar SGR 1806-20 produced the largest burst of energy in the Galaxy ever experimentally recorded on 27 December 2004^[10]
• PSR B1931+24 "... appears as a normal pulsar for about a week and then 'switches off' for about one month before emitting pulses again. [..] this pulsar slows down more rapidly when the pulsar is on than when it is off. [.. the] braking mechanism must be related to the radio emission and the processes creating it and the additional slow-down can be explained by a wind of particles leaving the pulsar's magnetosphere and carrying away rotational energy.^[11]
• PSR J1748-2446ad, at 716 Hz, the pulsar with the highest rotation speed.
• PSR J0108-1431, the closest known pulsar to the Earth. It lies in the direction of the constellation Cetus, at a distance of about 85 parsecs (280 light years). Nevertheless, it was not discovered until 1993 due to its extremely low luminosity. It was discovered by the Danish astronomer Thomas Tauris^[12] in collaboration with a team of Australian and European astronomers using the Parkes 64-meter radio telescope. The pulsar is 1000 times weaker than an average radio pulsar and thus this pulsar may represent the tip of an iceberg of a population of more than half a million such dim pulsars crowding our Milky Way.^[13][14]
• PSR J1903+0327, a ~2.15 ms pulsar discovered to be in a highly eccentric binary system with a sun-like star^[15].

The first radio pulsar, CP 1919, with a pulse period of 1. ... PSR 1919+21 is a pulsar with a period of 1. ... Year 1967 (MCMLXVII) was a common year starting on Sunday (link will display full calendar) of the 1967 Gregorian calendar. ... Nature is a prominent scientific journal, first published on 4 November 1869. ... Year 1968 (MCMLXVIII) was a leap year starting on Monday (link will display full calendar) of the Gregorian calendar. ... A binary pulsar is a pulsar with a binary companion, often another pulsar, white dwarf or neutron star. ... PSR B1913+16 is a pulsar in a binary star system, in orbit with another star around a common center of mass. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... It is believed that Cen X-3 is a pulsating X-ray source (X-ray pulsar) with a period of 4. ... A transient X-ray source first discovered in 1996 by the Italian BeppoSAX satellite, SAX J1808. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... PSR B1257+12 (sometimes abbreviated to PSR 1257+12) is a pulsar located 980 light years from Earth. ... Artists impression. ... In astronomy, SGR 1806-20 is a magnetar, a particular type of neutron star. ... December 27 is the 361st day of the year in the Gregorian calendar (362nd in leap years). ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... In astronomy, and in particular the study of pulsars, PSR J1748-2446ad is the fastest known spinning pulsar, at 716 Hz, the period being 0. ... Cetus (a name from Greek mythology, referring to a Whale or Sea monster, see Ceto) is a constellation of the southern sky, in the region known as the Water, near other watery constellations like Aquarius, Pisces, and Eridanus. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... Binary system may refer to one of the following. ...

Notes

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 52nd day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 169th day of the year (170th in leap years) in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance with the Gregorian calendar. ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ...

References

• Duncan R. Lorimer, "Binary and Millisecond Pulsars at the New Millennium", Living Rev. Relativity 4, (2001), http://www.livingreviews.org/lrr-2001-5
• D. R. Lorimer & M. Kramer; Handbook of Pulsar Astronomy; Cambridge Observing Handbooks for Research Astronomers, 2004
• Ingrid H. Stairs, "Testing General Relativity with Pulsar Timing", Living Rev. Relativity 6, (2003): http://www.livingreviews.org/lrr-2003-5
• Peter A. Sturrock; The UFO Enigma: A New Review of the Physical Evidence; Warner Books, 1999; ISBN 0-446-52565-0

External links

• A Pulsar Discovery - the detection of the first optical pulsar from the American Institute of Physics. Includes audio and teachers guides.
• The Discovery of Pulsars on H2G2
• Interview with Jocelyn Bell-Burnell on the discovery of pulsars (Jodcast) June, 2007 low quality version available
• The listing for the first pulsar (PULS CP 1919) in the Simbad database
• The ATNF Pulsar Catalogue
• Scientists Can Predict Pulsar Starquakes (SpaceDaily) Jun 07, 2006
• List of pulsars in binary systems
• XMM-Newton Makes New Discoveries About Old Pulsars (SpaceDaily) Jul 27, 2006
• Hot New Idea: How Dead Stars Go Cold Ker Than (SPACE.com) 27 July 2006 06:16 am ET
• Animation of pulsar 2008-01-17 01:58:AM MST

H2G2 is also an acronym for the The Hitchhikers Guide to the Galaxy. ...

See also

Wikimedia Commons has media related to:

Pulsars

• Neutron star
• Radio pulsar
• X-ray pulsar
• Magnetar
• Millisecond pulsar
• Rotating radio transient
• Pulsar planets
• Aleksander Wolszczan