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118-414: The Crab Pulsar is one of very few pulsars to be identified optically. The optical pulsar is roughly 20 kilometres (12 mi) in diameter and has a rotational period of about 33  milliseconds , that is, the pulsar "beams" perform about 30 revolutions per second. The outflowing relativistic wind from the neutron star generates synchrotron emission , which produces the bulk of the emission from

236-538: A United States Air Force radar system in Alaska designed as an early warning system to detect intercontinental ballistic missiles. This source was later understood by Schisler to be the Crab Pulsar, after the news of Bell Burnell's initial pulsar discoveries was reported. However, Schisler's detection was not reported publicly for four decades due to the classified nature of the radar observations. The Crab Pulsar

354-576: A loudspeaker . The first wire recorder was the Telegraphone invented by Valdemar Poulsen in the late 1890s. Wire recorders for law and office dictation and telephone recording were made almost continuously by various companies (mainly the American Telegraphone Company) through the 1920s and 1930s. These devices were mostly sold as consumer technologies after World War II. Widespread use of wire recording occurred within

472-400: A newly commissioned radio telescope that she helped build. Initially dismissed as radio interference by her supervisor and developer of the telescope, Antony Hewish , the fact that the signals always appeared at the same declination and right ascension soon ruled out a terrestrial source. On November 28, 1967, Bell and Hewish using a fast strip chart recorder resolved the signals as

590-416: A tape deck , tape player or tape machine or simply a tape recorder , is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present-day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal. Tape-recording devices include

708-606: A Blattnerphone at Avenue House in September 1930 for tests, and used it to record King George V 's speech at the opening of the India Round Table Conference on 12 November 1930. Though not considered suitable for music the machine continued in use and was moved to Broadcasting House in March 1932, a second machine also being installed. In September 1932, a new model was installed, using 3 mm tape with

826-414: 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. The events leading to the formation of a pulsar begin when the core of a massive star is compressed during a supernova , which collapses into a neutron star. The neutron star retains most of its angular momentum , and since it has only a tiny fraction of its progenitor's radius, it

944-400: A database of known pulsar frequencies and locations. Similar to GPS , this comparison would allow the vehicle to calculate its position accurately (±5 km). The advantage of using X-ray signals over radio waves is that X-ray telescopes can be made smaller and lighter. Experimental demonstrations have been reported in 2018. Generally, the regularity of pulsar emission does not rival

1062-488: A double neutron star (neutron star binary) is formed. Otherwise, the spun-up neutron star is left with no companion and becomes a "disrupted recycled pulsar", spinning between a few and 50 times per second. The discovery of pulsars allowed astronomers to study an object never observed before, the neutron star . This kind of object is the only place where the behavior of matter at nuclear density can be observed (though not directly). Also, millisecond pulsars have allowed

1180-418: A dull, loosely mounted stylus, attached to a rubber diaphragm, carried the reproduced sounds through an ear tube to its listener. Both recording and playback styluses, mounted alternately on the same two posts, could be adjusted vertically so that several recordings could be cut on the same 3 ⁄ 16 -inch-wide (4.8 mm) strip. While the machine was never developed commercially, it somewhat resembled

1298-478: A knob fastened to a flywheel . The wax strip passed from one eight-inch reel around the periphery of a pulley (with guide flanges) mounted above the V-pulleys on the main vertical shaft, where it came in contact with either its recording or playback stylus . The tape was then taken up on the other reel. The sharp recording stylus, actuated by a vibrating mica diaphragm, cut the wax from the strip. In playback mode,

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1416-530: A model to predict the likely date of pulsar glitches with observational data from the Rossi X-ray Timing Explorer . They used observations of the pulsar PSR J0537−6910 , that is known to be a quasi-periodic glitching pulsar. However, no general scheme for glitch forecast is known to date. In 1992, Aleksander Wolszczan discovered the first extrasolar planets around PSR B1257+12 . This discovery presented important evidence concerning

1534-434: A patent application in 1931, Merle Duston, a Detroit radio engineer, created a tape recorder capable of recording both sounds and voice that used a low-cost chemically treated paper tape. During the recording process, the tape moved through a pair of electrodes which immediately imprinted the modulated sound signals as visible black stripes into the paper tape's surface. The audio signal could be immediately replayed from

1652-503: A patent for his invention in 1909. The celluloid film was inscribed and played back with a stylus, in a manner similar to the wax cylinders of Edison's gramophone. The patent description states that the machine could store six records on the same strip of film, side by side, and it was possible to switch between them. In 1912, a similar process was used for the Hiller talking clock . In 1932, after six years of developmental work, including

1770-428: A precise distance to the Crab Pulsar. Pulsar A pulsar (from pulsating radio source ) is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles . This radiation can be observed only when a beam of emission is pointing toward Earth (similar to the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and

1888-491: A pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation . The first extrasolar planets were discovered in 1992 around a pulsar, specifically PSR B1257+12 . In 1983, certain types of pulsars were detected that, at that time, exceeded the accuracy of atomic clocks in keeping time . Signals from the first discovered pulsar were initially observed by Jocelyn Bell while analyzing data recorded on August 6, 1967, from

2006-497: A pulsar. 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. Because of the dispersive nature of the interstellar plasma , lower-frequency radio waves travel through

2124-588: A recording time of 32 minutes. In 1933, the Marconi Company purchased the rights to the Blattnerphone, and newly developed Marconi-Stille recorders were installed in the BBC's Maida Vale Studios in March 1935. The quality and reliability were slightly improved, though it still tended to be obvious that one was listening to a recording. A reservoir system containing a loop of tape helped to stabilize

2242-662: A rotating neutron star with a magnetic field would emit radiation, and even noted that such energy could be pumped into a supernova remnant around a neutron star, such as the Crab Nebula . After the discovery of the first pulsar, Thomas Gold independently suggested a rotating neutron star model similar to that of Pacini, and explicitly argued that this model could explain the pulsed radiation observed by Bell Burnell and Hewish. In 1968, Richard V. E. Lovelace with collaborators discovered period P ≈ 33 {\displaystyle P\approx 33}  ms of

2360-525: A second pulsating source was discovered in a different part of the sky that the "LGM hypothesis" was entirely abandoned. Their pulsar was later dubbed CP 1919 , and is now known by a number of designators including PSR B1919+21 and PSR J1921+2153. Although CP 1919 emits in radio wavelengths , pulsars have subsequently been found to emit in visible light, X-ray , and gamma ray wavelengths. The word "pulsar" first appeared in print in 1968: An entirely novel kind of star came to light on Aug. 6 last year and

2478-548: A series of pulses, evenly spaced every 1.337 seconds. No astronomical object of this nature had ever been observed before. On December 21, Bell discovered a second pulsar, quashing speculation that these might be signals beamed at earth from an extraterrestrial intelligence . When observations with another telescope confirmed the emission, it eliminated any sort of instrumental effects. At this point, Bell said of herself and Hewish that "we did not really believe that we had picked up signals from another civilization, but obviously

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2596-405: A small, dense star consisting primarily of neutrons would result from a supernova . Based on the idea of magnetic flux conservation from magnetic main sequence stars, Lodewijk Woltjer proposed in 1964 that such neutron stars might contain magnetic fields as large as 10 to 10   gauss (=10 to 10   tesla ). In 1967, shortly before the discovery of pulsars, Franco Pacini suggested that

2714-416: A spacecraft navigation system independently, or be used in conjunction with satellite navigation. X-ray pulsar-based navigation and timing (XNAV) or simply pulsar navigation is a navigation technique whereby the periodic X-ray signals emitted from pulsars are used to determine the location of a vehicle, such as a spacecraft in deep space. A vehicle using XNAV would compare received X-ray signals with

2832-582: A strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, "crab" and "millicrab" are sometimes used as units of flux density. A millicrab corresponds to a flux density of about 2.4 × 10  erg  s cm ( 2.4 × 10 W/m ) in the 2–10  keV X-ray band, for a "crab-like" X-ray spectrum, which is roughly power-law in photon energy: I  ~  E . Very few X-ray sources ever exceed one crab in brightness. Pulsed emission up to 1.5 TeV has been detected from

2950-718: A test of general relativity in conditions of an intense gravitational field. Pulsar maps have been included on the two Pioneer plaques as well as the Voyager Golden Record . They show the position of the Sun , relative to 14 pulsars, which are identified by the unique timing of their electromagnetic pulses, so that Earth's position both in space and time can be calculated by potential extraterrestrial intelligence. Because pulsars are emitting very regular pulses of radio waves, its radio transmissions do not require daily corrections. Moreover, pulsar positioning could create

3068-454: A year. ABC agreed to let him use transcription discs for the 1946–47 season, but listeners complained about the sound quality. Crosby realised that Mullin's tape recorder technology would enable him to pre-record his radio show with high sound quality and that these tapes could be replayed many times with no appreciable loss of quality. Mullin was asked to tape one show as a test and was subsequently hired as Crosby's chief engineer to pre-record

3186-422: Is an alternative tentative explanation of the pulsar-like properties of these white dwarfs. In 2019, the properties of pulsars have been explained using a numerical magnetohydrodynamic model explaining was developed at Cornell University . According to this model, AE Aqr is an intermediate polar -type star, where the magnetic field is relatively weak and an accretion disc may form around the white dwarf. The star

3304-406: Is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star. The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation of

3422-475: Is in the propeller regime, and many of its observational properties are determined by the disc- magnetosphere interaction. A similar model for eRASSU J191213.9−441044 is supported by the results of its observations at ultraviolet wave lengths, which showed that its magnetic field strength does not exceed 50 MG. Initially pulsars were named with letters of the discovering observatory followed by their right ascension (e.g. CP 1919). As more pulsars were discovered,

3540-555: Is less effective at slowing the pulsar's rotation, so millisecond pulsars live for billions of years, making them the oldest known pulsars. Millisecond pulsars are seen in globular clusters, which stopped forming neutron stars billions of years ago. Of interest to the study of the state of the matter in a neutron star are the glitches observed in the rotation velocity of the neutron star. This velocity decreases slowly but steadily, except for an occasional sudden variation known as "glitch". One model put forward to explain these glitches

3658-467: Is observable as random wandering in the pulse frequency or phase. It is unknown whether timing noise is related to pulsar glitches . According to a study published in 2023, the timing noise observed in pulsars is believed to be caused by background gravitational waves . Alternatively, it may be caused by stochastic fluctuations in both the internal (related to the presence of superfluids or turbulence) and external (due to magnetospheric activity) torques in

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3776-494: Is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods . This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays . (See also centrifugal mechanism of acceleration .) Pulsars’ highly regular pulses make them very useful tools for astronomers. For example, observations of

3894-402: Is that they are the result of " starquakes " that adjust the crust of the neutron star. Models where the glitch is due to a decoupling of the possibly superconducting interior of the star have also been advanced. In both cases, the star's moment of inertia changes, but its angular momentum does not, resulting in a change in rotation rate. When two massive stars are born close together from

4012-563: Is the electron density of the ISM. The dispersion measure is used to construct models of the free electron distribution in the Milky Way . Additionally, density inhomogeneities in the ISM 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

4130-458: Is used for the capstan and one for driving the reels for playback, rewind, and fast forward. The storage of an analog signal on tape works well, but is not perfect. In particular, the granular nature of the magnetic material adds high-frequency noise to the signal, generally referred to as tape hiss . Also, the magnetic characteristics of tape are not linear . They exhibit a characteristic hysteresis curve, which causes unwanted distortion of

4248-465: Is usually called a tape recorder or – if it has no record functionality – a tape player , while one that requires external amplification for playback is usually called a tape deck (regardless of whether it can record). Multitrack technology enabled the development of modern art music and one such artist, Brian Eno , described the tape recorder as "an automatic musical collage device." Magnetic tape brought about sweeping changes in both radio and

4366-750: The Crab Nebula pulsar using Arecibo Observatory . The discovery of the Crab pulsar provided confirmation of the rotating neutron star model of pulsars. The Crab pulsar 33- millisecond pulse period was too short to be consistent with other proposed models for pulsar emission. Moreover, the Crab pulsar is so named because it is located at the center of the Crab Nebula, consistent with the 1933 prediction of Baade and Zwicky. In 1974, Antony Hewish and Martin Ryle , who had developed revolutionary radio telescopes , became

4484-1123: The European Pulsar Timing Array (EPTA) in Europe, the Parkes Pulsar Timing Array (PPTA) in Australia, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) in Canada and the US, and the Indian Pulsar Timing Array (InPTA) in India. Together, the consortia form the International Pulsar Timing Array (IPTA). The pulses from Millisecond Pulsars (MSPs) are used as a system of galactic clocks. Disturbances in

4602-414: The nebula , seen from radio waves through to gamma rays . The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the surrounding nebula, forming a termination shock . The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from

4720-455: The reel-to-reel tape deck and the cassette deck , which uses a cassette for storage. The use of magnetic tape for sound recording originated around 1930 in Germany as paper tape with oxide lacquered to it. Prior to the development of magnetic tape, magnetic wire recorders had successfully demonstrated the concept of magnetic recording , but they never offered audio quality comparable to

4838-526: The 13.6-billion-year age of the universe, around 99% no longer pulsate. Though the general picture of pulsars as rapidly rotating neutron stars is widely accepted, Werner Becker of the Max Planck Institute for Extraterrestrial Physics said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work." Three distinct classes of pulsars are currently known to astronomers , according to

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4956-474: The 1950s. Consumer wire recorders were marketed for home entertainment or as an inexpensive substitute for commercial office dictation recorders, but the development of consumer magnetic tape recorders starting in 1946, with the BK 401 Soundmirror, using paper-based tape, gradually drove wire recorders from the market, being "pretty much out of the picture" by 1952. In 1924 a German engineer, Kurt Stille, developed

5074-634: The Brush Development Company in the United States, where work continued but attracted little attention until the late 1940s when the company released the very first consumer tape recorder in 1946: the Soundmirror BK 401. Several other models were quickly released in the following years. Tapes were initially made of paper coated with magnetite powder . In 1947/48 Minnesota Mining & Manufacturing Company ( 3M ) replaced

5192-619: The Crab Nebula in late 1968 by L. I. Matveenko in Soviet Astronomy . Optical pulsations were first reported by Cocke, Disney, and Taylor using the 36-inch (91 cm) telescope on Kitt Peak of the Steward Observatory of the University of Arizona. This observation had a audio tape recording the pulses and this tape also recorded the voices of John Cocke, Michael Disney and Bob McCallister (the night assistant) at

5310-494: The Crab pulsar. The only other known pulsar with emission in this energy range is the Vela Pulsar at 20 TeV. The Crab Nebula was identified as the remnant of SN 1054 by 1939. Astronomers then searched for the nebula's central star . There were two candidates, referred to in the literature as the "north following" and "south preceding" stars. In September 1942, Walter Baade ruled out the "north following" star but found

5428-525: The EMI TR90 and a Philips machine which was lightweight but very easy and quick to use. Bush House used several Leevers-Rich models. The Studer range of machines had become pretty well the studio recording industry standard by the 1970s, and gradually these replaced the aging BTR2s in recording rooms and studios. By the mid-2000s tape was pretty well out of use and had been replaced by digital playout systems. The typical professional audio tape recorder of

5546-519: The Poulsen wire recorder as a dictating machine. The following year a fellow German, Louis Blattner , working in Britain, licensed Stille's device and started work on a machine which would instead record on a magnetic steel tape, which he called the Blattnerphone. The tape was 6 mm wide and 0.08 mm thick, traveling at 5 feet per second; the recording time was 20 minutes. The BBC installed

5664-639: The ability to pre-record their broadcasts with the high quality of tape, and the recording ban was lifted. Crosby invested $ 50,000 of his own money into the Californian electronics company Ampex , and the six-man concern (headed by Alexander M. Poniatoff , whose initials became part of the company name) soon became the world leader in the development of tape recording, with its Model 200 tape deck, released in 1948 and developed from Mullin's modified Magnetophons. The BBC acquired some Magnetophon machines in 1946 on an experimental basis, and they were used in

5782-423: The amplitude of gravitational waves that a pulsar can emit, assuming that all the losses in energy are converted to gravitational waves . No gravitational waves observed at the expected amplitude and frequency (after correcting for the expected Doppler shift ) proves that other mechanisms must be responsible for the loss in energy. The non-observation so far is not totally unexpected, since physical models of

5900-460: The arrival time of pulses at 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

6018-455: The broadcasts had to be transcriptions, but their audio quality was indistinguishable from that of a live broadcast and their duration was far longer than was possible even with 16 rpm transcription discs. In the final stages of the war in Europe, the Allies' capture of a number of German Magnetophon recorders from Radio Luxembourg aroused great interest. These recorders incorporated all

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6136-436: The clocks will be measurable at Earth. A disturbance from a passing gravitational wave will have a particular signature across the ensemble of pulsars, and will be thus detected. The pulsars listed here were either the first discovered of its type, or represent an extreme of some type among the known pulsar population, such as having the shortest measured period. Tape recorder An audio tape recorder , also known as

6254-426: The coils of the tape head creates a fluctuating magnetic field. This causes the magnetic material on the tape, which is moving past and in contact with the head, to align in a manner proportional to the original signal. The signal can be reproduced by running the tape back across the tape head, where the reverse process occurs – the magnetic imprint on the tape induces a small current in the read head which approximates

6372-607: The crab nebula that could be coincident with it" using the 300-foot (91 m) Green Bank radio antenna . They were given the designations NP 0527 and NP 0532. The period of 33 milliseconds and location of the Crab Nebula pulsar NP 0532 was discovered by Richard V. E. Lovelace and collaborators on 10 November 1968, at the Arecibo Radio Observatory . The discovery of the pulsar with such a short period proved that pulsars are rotating neutron stars (not pulsating white dwarfs, as many scientists suggested). Soon after

6490-463: The curved space-time around Sgr A* , the supermassive black hole at the center of the Milky Way, could serve as probes of gravity in the strong-field regime. Arrival times of the pulses would be affected by special - and general-relativistic Doppler shifts and by the complicated paths that the radio waves would travel through the strongly curved space-time around the black hole. In order for

6608-610: The decades spanning from 1940 until 1960, following the development of inexpensive designs licensed internationally by the Brush Development Company of Cleveland, Ohio and the Armour Research Foundation of the Armour Institute of Technology (later Illinois Institute of Technology ). These two organizations licensed dozens of manufacturers in the U.S., Japan, and Europe. Wire was also used as a recording medium in black box voice recorders for aviation in

6726-519: The decision of the Nobel prize committee. In 1943, 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

6844-543: The discovery of the Crab Pulsar, David Richards discovered (using the Arecibo Telescope) that it spins down and, therefore, loses its rotational energy. Thomas Gold has shown that the pulsar's spin-down power is sufficient to power the Crab Nebula. A subsequent study by them, including William D. Brundage, also found that the NP 0532 source is located at the Crab Nebula. A radio source was also reported coincident with

6962-1166: The early 1950s used 1 ⁄ 4  in (6 mm) wide tape on 10 + 1 ⁄ 2  in (27 cm) reels, with a capacity of 2,400 ft (730 m). Typical speeds were initially 15 in/s (38.1 cm/s) yielding 30 minutes' recording time on a 2,400 ft (730 m) reel. Early professional machines used single-sided reels but double-sided reels soon became popular, particularly for domestic use. Tape reels were made from metal or transparent plastic. Standard tape speeds varied by factors of two: 15 and 30 in/s were used for professional audio recording; 7 + 1 ⁄ 2  in/s (19.1 cm/s) for home audiophile prerecorded tapes; 7 + 1 ⁄ 2 and 3 + 3 ⁄ 4  in/s (19.1 and 9.5 cm/s) for audiophile and consumer recordings (typically on 7 in (18 cm) reels). 1 + 7 ⁄ 8  in/s (4.8 cm/s) and occasionally even 15 ⁄ 16  in/s (2.4 cm/s) were used for voice, dictation, and applications where very long recording times were needed, such as logging police and fire department calls. The 8-track tape standard, developed by Bill Lear in

7080-488: The early stages of the new Third Programme to record and play back performances of operas from Germany. Delivery of tape was preferred as live relays over landlines were unreliable in the immediate post-war period. These machines were used until 1952, though most of the work continued to be done using the established media. In 1948, a new British model became available from EMI: the BTR1. Though in many ways clumsy, its quality

7198-412: The effect as scintillation , despite the woman's protestation that as a qualified pilot she understood scintillation and this was something else. Bell Burnell notes that the 30 Hz frequency of the Crab Nebula optical pulsar is difficult for many people to see. In 2007, it was reported that Charles Schisler detected a celestial source of radio emission in 1967 at the location of the Crab Nebula, using

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7316-431: The effects of general relativity to be measurable with current instruments, pulsars with orbital periods less than about 10 years would need to be discovered; such pulsars would orbit at distances inside 0.01 pc from Sgr A*. Searches are currently underway; at present, five pulsars are known to lie within 100 pc from Sgr A*. There are four consortia around the world which use pulsars to search for gravitational waves :

7434-452: The era, transcription discs and wire recorders , could not provide anywhere near this level of quality and functionality. Since some early refinements improved the fidelity of the reproduced sound, magnetic tape has been the highest quality analog recording medium available. As of the first decade of the 21st century, analog magnetic tape has been largely replaced by digital recording technologies. The earliest known audio tape recorder

7552-483: The evidence inconclusive for the "south preceding" star. Rudolf Minkowski , in the same issue of The Astrophysical Journal as Baade, advanced spectral arguments claiming that the "evidence admits, but does not prove, the conclusion that the south preceding star is the central star of the nebula". In late 1968, David H. Staelin and Edward C. Reifenstein III reported the discovery of two rapidly varying radio sources "near

7670-594: The first astronomers to be awarded the Nobel Prize in Physics , with the Royal Swedish Academy of Sciences noting that Hewish played a "decisive role in the discovery of pulsars". Considerable controversy is associated with the fact that Hewish was awarded the prize while Bell, who made the initial discovery while she was his PhD student, was not. Bell claims no bitterness upon this point, supporting

7788-437: The first widespread sound recording technology, used for both entertainment and office dictation. However, recordings on wax cylinders were unable to be easily duplicated, making them both costly and time consuming for large scale production. Wax cylinders were also unable to record more than 2 minutes of audio, a problem solved by gramophone discs . Franklin C. Goodale adapted movie film for analog audio recording. He received

7906-425: The flutter the more noise that can be heard causing the quality of the recording to be worse. Higher tape speeds used in professional recorders are prone to cause head bumps , which are fluctuations in low-frequency response. There is a wide variety of tape recorders in existence, from small hand-held devices to large multitrack machines. A machine with built-in speakers and audio power amplification to drive them

8024-403: The idea had crossed our minds and we had no proof that it was an entirely natural radio emission. It is an interesting problem—if one thinks one may have detected life elsewhere in the universe, how does one announce the results responsibly?" Even so, they nicknamed the signal LGM-1 , for " little green men " (a playful name for intelligent beings of extraterrestrial origin ). It was not until

8142-527: The innovative pop music studio-as-an-instrument recordings of artists such as Frank Zappa , the Beatles , and the Beach Boys . Philips advertised their reel-to-reel recorders as an audial family album and pushed families to purchase these recorders to capture and relive memories forever. But the use for recording music slowly but steadily rose as the main function for the tape recorder. Tape enabled

8260-577: The introduction of the first commercial tape recorder, the Ampex 200 model, launched in 1948, the invention of the first multitrack tape recorder , brought about another technical revolution in the recording industry. Tape made possible the first sound recordings totally created by electronic means, opening the way for the bold sonic experiments of the Musique Concrète school and avant-garde composers like Karlheinz Stockhausen , which in turn led to

8378-538: The key technological features of modern analog magnetic recording and were the basis for future developments in the field. Development of magnetic tape recorders in the late 1940s and early 1950s is associated with the Brush Development Company and its licensee, Ampex . The equally important development of the magnetic tape medium itself was led by Minnesota Mining and Manufacturing (3M) corporation. In 1938, S.J. Begun left Germany and joined

8496-419: The letter code became unwieldy, and so the convention then arose of using 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+16.7). Pulsars appearing very close together sometimes have letters appended (e.g. PSR 0021−72C and PSR 0021−72D). The modern convention prefixes

8614-455: The major radio networks didn't permit the use of disc recording in many programs because of their comparatively poor sound quality. Crosby disliked the regimentation of live broadcasts 39 weeks a year, preferring the recording studio's relaxed atmosphere and ability to retain the best parts of a performance. He asked NBC to let him pre-record his 1944–45 series on transcription discs , but the network refused, so Crosby withdrew from live radio for

8732-461: The medium slower 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: where D {\displaystyle D} is the distance from the pulsar to the observer, and n e {\displaystyle n_{e}}

8850-569: The mid-1960s, popularized consumer audio playback in automobiles in the USA. Eventually, this standard was replaced by the smaller and more reliable Compact Cassette , which was launched earlier in 1963. Philips 's development of the Compact Cassette in 1963 and Sony 's development of the Walkman in 1979 led to widespread consumer use of magnetic audio tape. In 1990, the Compact Cassette

8968-506: The modern magnetic tape recorder in its design. The tapes and machine created by Bell's associates, examined at one of the Smithsonian Institution 's museums, became brittle, and the heavy paper reels warped. The machine's playback head was also missing. Otherwise, with some reconditioning, they could be placed into working condition. The waxed tape recording medium was later refined by Edison's wax cylinder , and became

9086-514: The neutron star, which leads to the "pulsed" nature of its appearance. In rotation-powered pulsars, the beam is the result of the rotational energy of the neutron star, which generates an electrical field and very strong magnetic field, resulting in the acceleration of protons and electrons on the star surface and the creation of an electromagnetic beam emanating from the poles of the magnetic field. Observations by NICER of PSR J0030+0451 indicate that both beams originate from hotspots located on

9204-439: 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 . As this matter lands on the neutron star, it is thought to "bury" the magnetic field of the neutron star (although the details are unclear), leaving millisecond pulsars with magnetic fields 1000–10,000 times weaker than average pulsars. This low magnetic field

9322-430: 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

9440-498: The original signal and is then amplified for playback. Many tape recorders are capable of recording and playing back simultaneously by means of separate record and playback heads. Modern professional recorders usually use a three-motor scheme. One motor with a constant rotational speed drives the capstan . Usually combined with a rubber pinch roller, it ensures that the tape speed does not fluctuate. The other two motors, which are called torque motors, apply equal and opposite torques to

9558-461: The other recording and broadcast standards of the time. This German invention was the start of a long string of innovations that have led to present-day magnetic tape recordings. Magnetic tape revolutionized both the radio broadcast and music recording industries. It gave artists and producers the power to record and re-record audio with minimal loss in quality as well as edit and rearrange recordings with ease. The alternative recording technologies of

9676-406: The paper backing with cellulose acetate or polyester , and coated it first with black oxide, and later, to improve signal-to-noise ratio and improve overall superior quality, with red oxide ( gamma ferric oxide ). American audio engineer John T. Mullin and entertainer Bing Crosby were key players in the commercial development of magnetic tape. Mullin served in the U.S. Army Signal Corps and

9794-432: The presence of background gravitational waves. Scientists are currently attempting to resolve these possibilities by comparing the deviations seen between several different pulsars, forming what is known as a pulsar timing array . The goal of these efforts is to develop a pulsar-based time standard precise enough to make the first ever direct detection of gravitational waves. In 2006, a team of astronomers at LANL proposed

9912-536: The pulsar into the main body of the nebula. The period of the pulsar's rotation is increasing by 38  nanoseconds per day due to the large amounts of energy carried away in the pulsar wind. The Crab Nebula is often used as a calibration source in X-ray astronomy . It is very bright in X-rays , and the flux density and spectrum are known to be constant, with the exception of the pulsar itself. The pulsar provides

10030-557: The pulsar soon confirmed this prediction, providing the first ever evidence of the existence of gravitational waves. As of 2010, 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. In 1982, Don Backer led a group that discovered PSR B1937+21 , a pulsar with a rotation period of just 1.6 milliseconds (38,500 rpm ). Observations soon revealed that its magnetic field

10148-465: The radio industry for the first time to pre-record many sections of program content such as advertising, which formerly had to be presented live, and it also enabled the creation and duplication of complex, high-fidelity, long-duration recordings of entire programs. It also, for the first time, allowed broadcasters, regulators and other interested parties to undertake comprehensive logging of radio broadcasts for legislative and commercial purposes, leading to

10266-426: 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

10384-411: The recording industry. Sound could be recorded, erased and re-recorded on the same tape many times, sounds could be duplicated from tape to tape with only minor loss of quality, and recordings could now be very precisely edited by physically cutting the tape and rejoining it. In August 1948, Los Angeles-based Capitol Records became the first recording company to use the new process. Within a few years of

10502-509: The rest of the series. Crosby's season premier on 1 October 1947 was the first magnetic tape broadcast in America. He became the first major American music star to use tape to pre-record radio broadcasts, and the first to master commercial recordings on tape. The taped Crosby radio shows were painstakingly edited through tape-splicing to give them a pace and flow that was wholly unprecedented in radio. Soon other radio performers were demanding

10620-416: The rotational symmetry of pulsars puts a more realistic upper limit on the amplitude of gravitational waves several orders of magnitude below the spin-down limit. It is hoped that with the improvement of the sensitivity of gravitational wave instruments and the use of longer stretches of data, gravitational waves emitted by pulsars will be observed in future . The only other pulsar for which the spin-down limit

10738-507: The same cloud of gas, they can form a binary system and orbit each other from birth. If those two stars are at least a few times as massive as the Sun, their lives will both end in supernova explosions. The more massive star explodes first, leaving behind a neutron star. If the explosion does not kick the second star away, the binary system survives. The neutron star can now be visible as a radio pulsar, and it slowly loses energy and spins down. Later,

10856-513: The same recorder unit, which also contained photoelectric sensors, somewhat similar to the various sound-on-film technologies of the era. Magnetic recording was conceived as early as 1878 by the American engineer Oberlin Smith and demonstrated in practice in 1898 by Danish engineer Valdemar Poulsen . Analog magnetic wire recording , and its successor, magnetic tape recording, involve

10974-403: The second star can swell up, allowing the neutron star to suck up its matter. The matter falling onto the neutron star spins it up and reduces its magnetic field. This is called "recycling" because it returns the neutron star to a quickly-spinning state. Finally, the second star also explodes in a supernova, producing another neutron star. If this second explosion also fails to disrupt the binary,

11092-521: The signal. Some of this distortion is overcome by using inaudible high-frequency AC bias when recording. The amount of bias needs careful adjustment for best results as different tape material requires differing amounts of bias. Most recorders have a switch to select this. Additionally, systems such as Dolby noise reduction systems have been devised to ameliorate some noise and distortion problems. Variations in tape speed cause wow and flutter . Flutter can be reduced by using dual capstans. The higher

11210-409: The small scale variations in the ISM. Due to the high velocity (up to several hundred km/s) of many pulsars, a single pulsar scans the ISM rapidly, which results in changing scintillation patterns over timescales of a few minutes. The exact cause of these density inhomogeneities remains an open question, with possible explanations ranging from turbulence to current sheets . Pulsars orbiting within

11328-464: The source of the power of the electromagnetic radiation: Although all three classes of objects are neutron stars, their observable behavior and the underlying physics are quite different. There are, however, some connections. For example, X-ray pulsars are probably old rotationally-powered pulsars that have already lost most of their energy, and have only become visible again after their binary companions had expanded and begun transferring matter on to

11446-408: The south pole and that there may be more than two such hotspots on that star. This rotation slows down over time as electromagnetic power is emitted. When a pulsar's spin period slows down sufficiently, the radio pulsar mechanism is believed to turn off (the so-called "death line"). This turn-off seems to take place after about 10–100 million years, which means of all the neutron stars born in

11564-511: The speed of the recording. Despite these drawbacks, the ability to make replayable recordings proved useful, and even with subsequent methods coming into use (direct-cut discs and Philips-Miller optical film the Marconi-Stilles remained in use until the late 1940s. Magnetic tape recording as we know it today was developed in Germany during the 1930s at BASF (then part of the chemical giant IG Farben ) and AEG in cooperation with

11682-404: The speed. The tape was 3 mm wide and traveled at 1.5  meters/second. They were not easy to handle. The reels were heavy and expensive and the steel tape has been described as being like a traveling razor blade. The tape was liable to snap, particularly at joints, which at 1.5  meters/second could rapidly cover the floor with loops of the sharp-edged tape. Rewinding was done at twice

11800-420: The stability of atomic clocks . They can still be used as external reference. For example, J0437−4715 has a period of 0.005 757 451 936 712 637  s with an error of 1.7 × 10  s . This stability allows millisecond pulsars to be used in establishing ephemeris time or in building pulsar clocks . Timing noise is the name for rotational irregularities observed in all pulsars. This timing noise

11918-498: The standard in recording rooms for many years and was in use until the end of the 1960s. In 1963, the Beatles were allowed to enhance their recordings at the BBC by overdubbing. The BBC didn't have any multi-track equipment; Overdubbing was accomplished by copying onto another tape. The tape speed was eventually standardized at 15  ips for almost all work at Broadcasting House, and at 15 ips for music and 7½ ips for speech at Bush House. Broadcasting House also used

12036-536: The state radio RRG . This was based on Fritz Pfleumer 's 1928 invention of paper tape with oxide powder lacquered onto it. The first practical tape recorder from AEG was the Magnetophon K1 , demonstrated in Berlin, Germany in 1935. Eduard Schüller  [ de ] of AEG built the recorders and developed a ring-shaped recording and playback head. It replaced the needle-shaped head which tended to shred

12154-516: The supply and take-up reels during recording and playback functions and maintain the tape's tension. During fast winding operations, the pinch roller is disengaged and the take-up reel motor produces more torque than the supply motor. The cheapest models use a single motor for all required functions; the motor drives the capstan directly and the supply and take-up reels are loosely coupled to the capstan motor with slipping belts, gears, or clutches. There are also variants with two motors, in which one motor

12272-710: The tape. Friedrich Matthias of IG Farben/BASF developed the recording tape, including the oxide, the binder, and the backing material. Walter Weber, working for Hans Joachim von Braunmühl  [ de ] at the RRG, discovered the AC biasing technique, which radically improved sound quality. During World War II , the Allies noticed that certain German officials were making radio broadcasts from multiple time zones almost simultaneously. Analysts such as Richard H. Ranger believed that

12390-416: The time of the discovery. Their discovery was confirmed by Nather , Warner , and Macfarlane. Jocelyn Bell Burnell , who co-discovered the first pulsar PSR B1919+21 in 1967, relates that in the late 1950s a woman viewed the Crab Nebula source at the University of Chicago's telescope, then open to the public, and noted that it appeared to be flashing. The astronomer she spoke to, Elliot Moore, disregarded

12508-416: The use of a magnetizable medium which moves with a constant speed past a recording head. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal to be amplified and played back through

12626-547: 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. White dwarfs can also act as pulsars. Because the moment of inertia of a white dwarf is much higher than that of a neutron star, the white-dwarf pulsars rotate once every several minutes, far slower than neutron-star pulsars. By 2024, three pulsar-like white dwarfs have been identified. There

12744-453: Was Bing Crosby's technical director, Murdo Mackenzie. He arranged for Mullin to meet Crosby and in June 1947 he gave Crosby a private demonstration of his magnetic tape recorders. Bing Crosby , a top movie and singing star, was stunned by the amazing sound quality and instantly saw the huge commercial potential of the new machines. Live music was the standard for American radio at the time and

12862-464: Was a non-magnetic , non-electric version invented by Alexander Graham Bell 's Volta Laboratory and patented in 1886 ( U.S. patent 341,214 ). It employed a 3 ⁄ 16 -inch-wide (4.8 mm) strip of wax-covered paper that was coated by dipping it in a solution of beeswax and paraffin and then had one side scraped clean, with the other side allowed to harden. The machine was of sturdy wood and metal construction and hand-powered by means of

12980-401: Was a chance visit to a studio at Bad Nauheim near Frankfurt while investigating radio beam rumors, that yielded the real prize. Mullin was given two suitcase-sized AEG 'Magnetophon' high-fidelity recorders and fifty reels of recording tape. He had them shipped home and over the next two years he worked on the machines constantly, modifying them and improving their performance. His major aim

13098-414: Was broken so far is the Vela Pulsar . In 2019 the Crab Nebula , and presumably therefore the Crab Pulsar, was observed to emit gamma rays in excess of 100  TeV , making it the first identified source of ultra-high-energy cosmic rays . In 2023, Very long baseline interferometry (VLBI) was used to conduct precision astrometry using the radio giant-pulse emission of the Crab Pulsar, thus measuring

13216-490: Was good, and as it wasn't possible to obtain any more Magnetophons it was an obvious choice. In the early 1950s, the EMI BTR 2 became available; a much-improved machine and generally liked. The machines were responsive, could run up to speed quite quickly, had light-touch operating buttons, forward-facing heads (The BTR 1s had rear-facing heads which made editing difficult), and were quick and easy to do fine editing. It became

13334-403: 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 rivaling the stability of the best atomic clocks on Earth. Factors affecting

13452-476: Was posted to Paris in the final months of WWII. His unit was assigned to find out everything they could about German radio and electronics, including the investigation of claims that the Germans had been experimenting with high-energy directed radio beams as a means of disabling the electrical systems of aircraft. Mullin's unit soon amassed a collection of hundreds of low-quality magnetic dictating machines, but it

13570-469: Was referred to, by astronomers, as LGM (Little Green Men). Now it is thought to be a novel type between a white dwarf and a neutron [star]. The name Pulsar is likely to be given to it. Dr. A. Hewish told me yesterday: '... I am sure that today every radio telescope is looking at the Pulsars.' The existence of neutron stars was first proposed by Walter Baade and Fritz Zwicky in 1934, when they argued that

13688-465: Was the dominant format in mass-market recorded music. The development of Dolby noise reduction technology in the 1960s brought audiophile-quality recording to the Compact Cassette also contributing to its popularity. Since their first introduction, analog tape recorders have experienced a long series of progressive developments resulting in increased sound quality, convenience, and versatility. Due to electromagnetism , electric current flowing in

13806-516: Was the first pulsar for which the spin-down limit was broken using several months of data of the LIGO observatory. Most pulsars do not rotate at constant rotation frequency, but can be observed to slow down at a very slow rate (3.7 × 10 Hz/s in case of the Crab). This spin-down can be explained as a loss of rotation energy due to various mechanisms. The spin-down limit is a theoretical upper limit of

13924-467: Was to interest Hollywood studios in using magnetic tape for movie soundtrack recording. Mullin gave two public demonstrations of his machines, and they caused a sensation among American audio professionals; many listeners literally could not believe that what they heard was not a live performance. By luck, Mullin's second demonstration was held at MGM Studios in Hollywood and in the audience that day

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