Crab Nebula

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Supernova remnant
Crab Nebula data
Crab Nebula, image from the Hubble Space Telescope
Crab Nebula, image from the Hubble Space Telescope
Constellation bull
Position
equinox : J2000.0
Right ascension 05h 34m 32.0s
declination + 22 ° 00 ′ 52 ″
Further data
Brightness  (visual)

8.4 mag

Angular expansion

6 ′ × 4 ′

distance

6300 ly

diameter 6 × 4 years
history
discovery

John Bevis

Date of discovery

1731

Catalog names
M  1 • NGC  1952 • IRAS  05314 + 2200 • Sh 2–244
Aladin previewer

The Crab Nebula (rare Crab Nebula , formerly also Crab Nebula from English Crab Nebula , cataloged as M 1 and NGC 1952 ) in the constellation Taurus is the remnant of the supernova observed in 1054 , in which a pulsar wind nebula was formed. It is located in the Perseus arm of the Milky Way and is about 2000 parsecs from Earth.

The nebula, which is expanding at almost 1500 kilometers per second, is oval in shape with a length of 6 arc minutes and a width of 4 arc minutes. In its center is the neutron star that emerged from the exploded original star , which rotates about 30 times per second (33 ms period) around its axis and is detectable as a pulsar in the radio frequency range as well as in the optical, X-ray and gamma frequency range (so-called cancer or crab pulsar ) is. The surrounding nebula is criss-crossed by filaments that have arisen from the outer shells of the original star and consist for the most part of ionized hydrogen and helium . In addition, there are smaller proportions of carbon , oxygen , nitrogen , iron , neon and sulfur , sometimes also in the form of dust.

Because of its low apparent brightness , the Crab Nebula can only be observed through telescopes and was only discovered with their systematic use in the 18th century. Due to its proximity and as one of the youngest galactic pulsar wind nebulae, it has since been one of the most intensively researched objects in astronomy .

exploration

Discovery and appearance of the nebula

The nebula-like appearance was discovered in 1731 by John Bevis while making star maps and, independently, by Charles Messier in search of comets in August 1758. While the discovery of Bevis remained unpublished for a long time, it was the trigger for Messier to compile his catalog of nebulae and star clusters in which the Crab Nebula is classified as the first object. Its shape is described as resembling a candle flame .

Sketch of the Crab Nebula, Lord Rosse , 1844
Isaac Roberts ' image of the Crab Nebula, 1895

John Herschel published an illustration of the nebula in 1833, which showed the nebula as an oval star cluster - a structure that he mistakenly suspected because of a mottling he recognized. Lord Rosse was the fog with its large reflecting telescope observing in detail and published a drawing in 1844. He is also the designation as the Crab Nebula often attributed, but the resemblance was filaments with the extremities of a cancer that is particularly pronounced in this drawing, of Thomas Romney Robinson mentioned earlier. Towards the end of the 19th century, Isaac Roberts , a pioneer of astrophotography , published the first images of the Crab Nebula and found that the nebula in his images did not resemble the previously known drawings.

Spectroscopic investigations by Vesto Slipher in the 1910s showed, based on characteristic spectral lines , that the nebula consists of hydrogen and helium . He noticed that these spectral lines are split and suspected the Stark effect to be the cause. Shortly thereafter, Roscoe Frank Sanford considered that opposing Doppler shifts with speeds of −600 to −1000 km / s and 1620 to 1750 km / s also explain the split. During his investigations, he also recognized that the brightest area glows blue and has a continuous spectrum. These results were later confirmed by Walter Baade through recordings with narrow-band filters, which also showed that the light bluish area lies in the center and made up about 80% of the brightness of the nebula, while the line spectra originated from the filaments.

In 1921, Carl Otto Lampland discovered on the basis of recordings from different times in the past that the structure, especially in the center of the Crab Nebula, changes over time - a property that, with three different exceptions, was not found in any other nebula .

Supernova

Inspired by the discovery of Lampland, John Charles Duncan confirmed the change in the Crab Nebula shortly afterwards on the basis of further recordings and also recognized that the change in the outer area is an expansion. At the same time, Knut Lundmark noticed that the Crab Nebula is close to the Nova from the year 1054 recorded in Chinese writings . Seven years later, in 1928, Edwin closed Hubble by calculating the expansion back to this nova some 900 years ago.

Around ten years later, Nicholas Ulrich Mayall determined the actual expansion speed as 1300 km / s using the Doppler splitting of the spectral lines and determined the distance of 1500 parsecs (4900 light years ) by comparison with the apparent expansion . Walter Baade and Knut Lundmark then recognized that, due to the great distance together with the high brightness observed in 1054, it must be a so-called supernova, the Crab Nebula emerged from a star: Walter Baade had together with Fritz just a few years earlier Zwicky postulates that next to a nova there can be a much more luminous, but rarer “super nova”. Here a massive star explodes, forming an expanding nebula from its outer layers while its core collapses into a neutron star .

The neutron star suspected in the center of the nebula was confirmed by spectroscopic studies by Rudolph Minkowski in the early 1940s. The spectroscopy indicated a solar mass with a diameter of at most 2% of the sun and thus at least 180,000 times the density and - what distinguishes it from a white dwarf - a temperature of 500,000 Kelvin and 30,000 times the luminosity of the sun . This luminosity results from the observed luminosity of the entire nebula under the assumption that the neutron star outside the visible spectrum supplies it with the energy; in the visible spectrum the neutron star only reaches 16  mag .

Minkowski assigned the supernova to Type I according to a phenomenological classification system he had designed shortly before. However, with the gradual refinement and addition of physical models, the type II-P became more and more plausible.

Synchrotron radiation

In 1948, John Gatenby Bolton and other scientists found the Taurus A radio source at the position of the nebula and realized that the high intensity is probably not caused by thermal processes. Shortly thereafter, Hannes Alfvén and Nicolai Herlofson suggested synchrotron radiation as an explanation, which is caused by electrons in a strong magnetic field that are almost light-fast . In 1953 Iosef Shklovsky suspected that the blue glow of the center is also caused by synchrotron radiation and that this is polarized due to the magnetic field. This polarization was detected the following year, but the source of the electrons and the magnetic field remained the subject of controversy for a long time.

Gamma radiation from the celestial sphere : in the center of the image the galactic center ; far right, bright, the Crab Nebula

The first X-ray astronomical observations , which are only possible outside the atmosphere , were carried out with Aerobee rockets from 1963 . Initially only two very bright X-ray sources were discovered in the energy range between 1.5 keV and 8 keV and the cancer nebula was identified with one of them, Taurus X-1. This also gave evidence for the neutron star as the cause of the magnetic field. In 1967 it was recognized by instruments on an altitude balloon that it was one of the strongest sources of gamma radiation in the range up to 560 keV. At this time, researchers began to study gamma radiation down to the teraelectron volt energy range with the help of Cherenkov telescopes , and this was demonstrated more and more clearly in the course of the 1970s. Observations with the Fermi Gamma-ray Space Telescope also showed an occasional strong flare-up of activity that lasted several days. In 2019, gamma radiation with over 100 TeV was detected from the Crab Nebula, making it the first known source of such radiation.

pulsar

Light curve and slow motion picture of the pulsar in the center of the Crab Nebula. Recording with a single quantum camera on the 80cm telescope of the Wendelstein Observatory, Dr. F. Fleischmann, 1998

In the mid-1960s, Lodewijk Woltjer considered that a neutron star could bundle the magnetic flux of the previous star into an extremely strong magnetic field. A little later, Franco Pacini concluded that if this star also retains the angular momentum of the previous star and rotates rapidly due to the contraction , it releases huge amounts of energy into the surrounding nebula like a dynamo .

Sequence of images of the Crab Nebula pulsar (right in the picture): slow motion of the main and secondary pulse, which is repeated every 33 ms

Motivated by the report in 1968 about the first pulsar  - such a neutron star that appears to pulsate - David H. Staelin and Edward C. Reifenstein scanned the sky and discovered two pulsating radio sources in the area of ​​the Crab Nebula - and possibly belonging to it. The discovery was made with the 90-meter radio telescope in Green Bank . They labeled the radio sources with NP 0527 and NP 0532. NP 0527 ultimately turned out to be significantly older than the supernova from the year 1054, but NP 0532 could be identified as belonging to the Crab Nebula. The pulse period of 33.09 ms and its slow increase could be determined shortly after the discovery with the help of the three times larger radio telescope at the Arecibo Observatory . A comparison showed that the neutron star rotating according to the observed pulsation with a magnetic field of 100,000,000 Tesla emits an output that corresponds to the rotational energy released by slowing down the rotation and at the same time to approximately the entire synchrotron radiation, assuming a pulsar diameter of 24 km lays; the Crab Nebula thus draws its energy from the gradually slower rotating neutron star like a flywheel .

The pulsation could also be detected in other spectral ranges. As early as 1969, the pulsar PSR B0531 + 21 was identified with the central star of the Crab Nebula in the optical area, and shortly afterwards in the same year also in the X-ray area. The pulses have a main pulse and a secondary pulse, the pulse shape and pulse height depending on the spectral range; with gamma radiation, the secondary pulse can be higher than the main pulse. There are different models of the pulsar that describe this radiation with these pulse shapes; in one, for example, the magnetic field is inclined by 45 ° to the axis of rotation and this is inclined by 67 ° to the direction of observation. However, the intensity of these pulses can occasionally be higher than that observed with very few other pulsars. These higher intensity pulses are known as giant pulses and occur with ten times the energy on average about every ten minutes, but can also occur with 2000 times the energy. Subsequent investigations showed that some of them contain sub-pulses only 2 nanoseconds long, so the emission range must be less than 1 meter. The mechanism of its formation has not yet been fully clarified.

X-rays from the Crab Nebula in the energy range 0.5–7.0 keV, Chandra Space Telescope

On the basis of the observations, Wallace Hampton Tucker already suspected in 1969 that a so-called pulsar wind from the charged particles, which are almost at the speed of light, would begin to glow when hitting the surrounding nebula, and five years later Martin John Rees and James Edward Gunn specified that the relativistic electrons and Positrons are created in the toroidal magnetic field around the pulsar and synchrotron radiation sets in as soon as they collide with the nebula. In addition, jets formed by the magnetic field from relativistic charged particles are formed along the axis of rotation , as was calculated in 1984. Around 10 years later, it was possible to detect these jets in the X-ray and optical areas using the high-resolution telescopes ROSAT , the Hubble space telescope and the Chandra space telescope .

Center of the Crab Nebula , superimposition of images in the areas of visible light (red) and X-rays (blue). You can see the embedded pulsar .

According to more recent studies, a diameter of 28 to 30 km is assumed for the pulsar in the Crab Nebula. This results in an energy output of a little more than 100,000 times that of the sun. The high amount of radiated energy generates the extremely dynamic region in the center of the Crab Nebula, discovered by Lampland, which can be observed in detail with the high-resolution Hubble Space Telescope and the Chandra Space Telescope: While most changes in astronomical objects happen so slowly that they can only be seen after many years, the inside of the Crab Nebula changes within a few days. The areas of greatest change in the inner part of the nebula are at the point where the pulsar's jets collide with the surrounding material and form a shock wave . Together with the equatorial wind, they appear as a series of clump-like structures that grow steeply, light up, and then fade as they move away from the pulsar and into the nebula.

Filaments

As early as 1942, Walter Baade reported on recordings of the filaments with narrow-band filters, with which he demonstrated their ionization through characteristic spectral lines of hydrogen . Through more detailed investigations of the also existing spectral lines of oxygen and helium, Donald Edward Osterbrock was able to determine their temperature with around 15,000 Kelvin and density with 550 to 3700 ionized particles per cubic centimeter in 1957, which further investigations confirmed. Shortly thereafter, it was assumed that the complex shape of the filaments was caused by a Rayleigh-Taylor instability at the interface between the neutron star and the ejected supernova remnant.

Recent research shows that the Crab Nebula is currently expanding at a speed of 1500 km / s. If one calculates the expansion back, one obtains a date for the formation of the nebula, which points to several decades after 1054. It seems as if the fog was expanding at an accelerated rate. It is believed that the energy required for the acceleration comes from the pulsar, which intensified the magnetic field, and that this caused the filaments to move faster away from the center. Differences in the calculated expansion of the filaments and the polar wind nebula also support the Rayleigh-Taylor instability as an explanation of the filament morphology.

Total mass

In the far infrared ( Herschel space telescope ), red, the dust distribution along the filaments becomes clear.

Estimates of the mass of the Crab Nebula were initially inconsistent. In 1942 Minkowski named another 15 solar masses for the surrounding nebula in addition to the approximately 1 solar mass for the neutron star. Osterbrock tried to determine the total mass of the filaments in 1957. The resulting value of a few percent of the solar mass, however, was not confirmed by subsequent investigations, which indicate that the mass of the sun is one to five times. From theoretical models of supernova explosions it was concluded that the star must have previously had a mass between eight and twelve solar masses . It was long suspected that the additional mass required for a supernova could lie in a shell around the Crab Nebula, which, however, was not found despite searches in different wavelengths. Taking into account the dust that could be observed in the far infrared with the Herschel space telescope , in 2015 a gas mass of seven solar masses and a dust mass of slightly less than one solar mass was concluded. Together with the pulsar, which has a little more than one solar mass, this results in a total of around nine solar masses. More recent analyzes, however, come to an order of magnitude smaller dust mass or a slightly larger total mass of 9.5–10 solar masses.

distance

Accurate determination of the removal of the Crab Nebula has proven difficult. The method for determining the distance described by Mayall in 1937 has been reproduced many times and, depending on the procedure chosen, delivered values ​​from 1030 parsecs to 2860 parsecs. On the basis of assumptions about the interstellar medium and the absorptions caused by this in different spectral ranges, a very similar range of values ​​was reached; physical reasons, such as the comparison with other supernovae or the intensity ratio of emission lines, speak for distances of 1800–2000 parsecs. Since a number of other established methods of determining distance fail due to the characteristics of the Crab Nebula, the value of 2000 ± 500 parsecs averaged by Virginia Trimble from the measurements mentioned around 1970 was often used. In 2018, with the aid of the Gaia space probe, an optical parallax determination was possible , which indicates a distance of more than 3000 parsecs and makes distances of less than 2400 parsecs seem unlikely.

Transit of bodies of the solar system

Color-coded animation of different spectral ranges:
red: radio range (VLA) ; yellow: IR (Spitzer Space Telescope) ; green: visible spectrum (HST) ; blue: UV (XMM-Newton) ; violet: gamma radiation (Chandra X-ray Observatory)

Since the Crab Nebula is only around 1.5 ° from the ecliptic , the moon and sometimes planets can seemingly cross or graze this nebula in the sky when viewed from Earth. The sun itself does not cross the fog, but its corona does . Such events help to better explore the nebula and the objects in front of the nebula by studying how the nebula's radiation changes.

Lunar transits were used to find the sources of the X-rays in the nebula. Before you had satellites like the Chandra X-Ray Observatory that could observe X- rays, X-ray observations were mostly low-resolution. However, when the moon moves in front of the nebula, the changes in brightness of the nebula can be used to map the X-ray emission of the nebula. When X-rays were first observed in the Crab Nebula, the moon, as it brushed the nebula in the sky, was used to pinpoint the exact location of the X-rays.

The solar corona obscures the Crab Nebula every June. Changes in the radio waves of the Crab Nebula reveal the density and structure of the solar corona. The first observations revealed that the solar corona is much more extensive than previously assumed; later observations showed that it exhibits considerable density fluctuations.

Saturn very rarely wanders past the nebula. Its transit on January 4, 2003 was the first since December 31,  1295 jul. ; the next will take place on August 5, 2267. With the help of the Chandra X-Ray Observatory, the Saturn moon Titan was examined more closely. It turned out that X-rays were also emitted around titanium. The reason lies in the absorption of X-rays in its atmosphere. This gave a value of 880 km for the thickness of Titan's atmosphere. The Saturn transit itself could not be observed because Chandra was crossing the Van Allen Belt at the time .

Observability

The Crab Nebula is best observed with telescopes from Europe in the winter months, as it is then far above the horizon: The culmination for 10 ° East is on January 4th at 11 p.m. In telescopes with a 50–75 mm aperture , it appears as an oval spot; further structures can be seen from 130 mm. The filaments only show up in a telescope with a 400 mm aperture with a good seeing of better than 2 arc seconds . Spectral filters for the O-III line highlight structures and polarization filters reveal the complex, spatially varying polarization effects.

There have been reports of observing the pulsar pulsation.

literature

  • Minas C. Kafatos, Richard BC Henry: The Crab Nebula and related supernova remnants. Cambridge University Press, Cambridge et al. 1985, ISBN 0-521-30530-6 .
  • Simon Mitton: The Crab Nebula. Faber and Faber, London 1979, ISBN 0-684-16077-3 .
  • Rodney Deane Davies, Francis Graham-Smith (Eds.): The Crab Nebula. Reidel, Dordrecht 1971, ISBN 978-94-010-3087-8 .

Web links

Commons : Messier 1  - album with pictures, videos and audio files
Wiktionary: Crab Nebula  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ NASA / IPAC EXTRAGALACTIC DATABASE
  2. ↑ a b Messier 1. In: messier.seds.org. August 22, 2007, accessed September 28, 2019 .
  3. ^ A b c Virginia Trimble : The Distance to the Crab Nebula and NP 0532 . In: Publications of the Astronomical Society of the Pacific . tape 85 , 1973, pp. 579-585 , bibcode : 1973PASP ... 85..579T .
  4. ↑ Crab Nebula . In: Meyer large conversation lexicon . tape 4 , 1903, pp. 329 ( archive.org ).
  5. ↑ ROSAT # active_time
  6. ↑ a b Michael F. Bietenholz, Richard L. Nugent: New expansion rate measurements of the Crab Nebula in radio and optical . In: Monthly Notices of the Royal Astronomical Society . tape 454 , no. 3 , 2015, p. 2416–2422 , bibcode : 2015MNRAS.454.2416B .
  7. ↑ Stephen P. Reynolds, Kazimierz J. Borkowski, Peter H. Gwynne: Expansion and Brightness Changes in the Pulsar-wind Nebula in the Composite Supernova Remnant Kes 75 . In: Astrophysical Journal . tape 856 , no. 2 , p. 1–12 , bibcode : 2018ApJ ... 856..133R .
  8. ↑ John Herschel : Observations of Nebulae and Clusters of Stars, Made at Slough, with a Twenty-Feet Reflector, between the Years 1825 and 1833 . In: Philosophical Transactions of the Royal Society of London . Volume II, 1833, pp. 359-505 , doi : 10.1098 / rstl.1833.0021 ( digitized, see Fig. 81 ).
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  10. ^ Isaac Roberts : Photographs of the Region of the "Crab" Nebula, 1 M. Tauri . In: Monthly Notices of the Royal Astronomical Society . tape 52 , 1892, p. 502 , bibcode : 1892MNRAS..52..502R .
  11. ^ Isaac Roberts: A Selection of Photographs of Stars, Star-clusters and Nebulae . Volume II. The Universal Press, London 1899, pp. 164 ( digitized ).
  12. ^ Vesto Melvin Slipher : Spectrographic Observations of Nebulae and Star Clusters . In: Publications of the Astronomical Society of the Pacific . tape 28 , 1916, pp. 191-192 . Digitized ( Memento from March 13, 2016 in the Internet Archive )
  13. ^ Roscoe Frank Sanford : Spectrum of the Crab Nebula . In: Publications of the Astronomical Society of the Pacific . tape 31 , no. 180 , 1919, pp. 108-109 , bibcode : 1919PASP ... 31..108S .
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  18. ^ Edwin Hubble : Novae or Temporary Stars . In: Astronomical Society of the Pacific Leaflet . tape 1 , no. 14 , 1928, pp. 55–58 , bibcode : 1928ASPL .... 1 ... 55H .
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  21. ^ Walter Baade, Fritz Zwicky : On Super-novae . In: Contributions from the Mount Wilson Observatory . tape 3 , 1934, pp. 73–78 , bibcode : 1934CoMtW ... 3 ... 73B .
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  24. ↑ Rudolph Minkowski: The Spectra of the Supernovae in IC 4182 and in NGC 1003 . In: Astrophysical Journal . tape 89 , 1939, pp. 156-217 , bibcode : 1939ApJ .... 89..156M .
  25. ↑ Roger A. Chevalier : What SN 1054 A Type II Supernova? 1977, p. 53-61 , bibcode : 1977ASSL ... 66 ... 53C .
  26. ↑ FS Kitaura, H.-Th. Janka, W. Hillebrandt: Explosions of O-Ne-Mg Cores, the Crab Supernova, and Subluminous Type II-P Supernovae . In: Astronomy and Astrophysics . tape 450 , no. 1 , 2006, p. 345-350 , bibcode : 2006A & A ... 450..345K .
  27. ^ Nathan Smith: The Crab Nebula and the class of Type IIn-P supernovae caused by sub-energetic electron capture explosions . In: Monthly Notices of the Royal Astronomical Society . tape 434 , no. 1 , 2013, p. 102–113 , bibcode : 2013MNRAS.434..102S .
  28. ↑ Takashi J. Moriya, Nozomu Tominaga, Norbert Langer, Ken'ichi Nomoto, Sergei I. Blinnikov, Elena I. Sorokina: Electron-capture supernovae exploding within their progenitor wind . In: Astronomy and Astrophysics . tape 569 , 2014, p. 1–8 , bibcode : 2014A & A ... 569A..57M .
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  30. ^ JG Bolton, GJ Stanley: The Position and Probable Identification of the Source of the Galactic Radio-Frequency Radiation Taurus-A . In: Australian Journal of Scientific Research A . tape 2 , 1949, p. 139–148 , bibcode : 1949AuSRA ... 2..139B .
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  32. ^ Iosef Shklovsky : On the Nature of the Crab Nebula's Optical Emission . In: Doklady Akademii Nauk SSSR . tape 90 , 1953, pp. 983 . Translated into English in Lang, KR, & Gingerich, O. 1979, A source book in astronomy and astrophysics, 1979
  33. ^ Jan Hendrik Oort , Theodore Walraven : Polarization and composition of the Crab nebula . In: Bulletin of the Astronomical Institutes of the Netherlands . tape 12 , p. 285–308 , bibcode : 1956BAN .... 12..285O .
  34. ^ JH Piddington: The Crab Nebula and the Origin of Interstellar Magnetic Fields . In: Australian Journal of Physics . tape 10 , 1957, pp. 530-546 , bibcode : 1957AuJPh..10..530P .
  35. ^ A b S. Bowyer , ET Byram, TA Chubb, H. Friedman : X-ray Sources in the Galaxy . In: Nature . tape 201 , no. 4926 , 1964, pp. 1307-1308 , bibcode : 1964Natur.201.1307B .
  36. ↑ a b Lodewijk Woltjer : X-Rays and Type I Supernova Remnants . In: Astrophysical Journal . tape 140 , 1964, pp. 1309-1313 , bibcode : 1964ApJ ... 140.1309W .
  37. ^ RC Haymes, DV Ellis, GJ Fishman, JD Kurfess, WH Tucker : Observation of Gamma Radiation from the Crab Nebula . In: Astrophysical Journal Letters . tape 151 , 1968, pp. L9-L14 , doi : 10.1086 / 180129 , bibcode : 1968ApJ ... 151L ... 9H .
  38. ^ JE Grindlay: Very high-energy gamma ray astronomy . In: NASA. Goddard Space Flight Center The Structure and Content of the Galaxy and Galactic Gamma Rays . 1977, p. 81-98 , bibcode : 1977NASCP ... 2 ... 81G .
  39. ↑ astronews.com: Surprising radiation from the Crab Nebula October 7, 2011
  40. ↑ astronews.com: High- energy radiation from the Crab Nebula January 14, 2016
  41. ↑ astronews.com: A spark in the pulsar wind November 22, 2017
  42. ↑ NASA's Fermi Spots 'Superflares' in the Crab Nebula
  43. ↑ M. Amenomori: First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source . In: Physical Review Letters . tape 123 , no. 5 , 2019, p. 051101 , arxiv : 1906.05521 , bibcode : 2019PhRvL.123e1101A .
  44. ^ A b Franco Pacini : Energy Emission from a Neutron Star . In: Nature . tape 216 , no. 5115 , 1967, pp. 567-568 , doi : 10.1038 / 216567a0 , bibcode : 1967Natur.216..567P .
  45. ↑ Thomas Gold : Rotating Neutron Stars as the Origin of the Pulsating Radio Sources . In: Nature . tape 218 , no. 5143 , 1968, pp. 731-732 , doi : 10.1038 / 218731a0 , bibcode : 1968Natur.218..731G .
  46. ^ David H. Staelin, Edward C. Reifenstein, III: Pulsating Radio Sources near Crab Nebula . In: International Astronomical Union Circulars . No. 2110 , 1968 ( archive.org ).
  47. ^ David H. Staelin, Edward C. Reifenstein, III: Pulsating radio sources near the Crab Nebula . In: Science . tape 162 , no. 3861 , 1968, pp. 1481–1483 , doi : 10.1126 / science.162.3861.1481 , PMID 17739779 , bibcode : 1968Sci ... 162.1481S , JSTOR : 1725616 .
  48. ^ DW Richards, JA Roberts: Timing of the Pulsar NP 0527 . In: Transactions of the International Astronomical Union . 1971, p. 211-216 , doi : 10.1017 / S0074180900007464 .
  49. ↑ RVE Lovelace, JM Sutton, HD Craft Jr .: Pulsar NP 0532 near Crab nebula . In: International Astronomical Union Circulars . No. 2113 , 1968 ( archive.org , see p. 4 [PDF]).
  50. ^ D. Richards: NP 0532 . In: International Astronomical Union Circulars . No. 2114 , 1968 ( archive.org ).
  51. ^ Jeremiah P. Ostriker , James E. Gunn : On the Nature of Pulsars. I. Theory . In: Astrophysical Journal . tape 157 , September 1969, p. 1395-1417 , bibcode : 1969ApJ ... 157.1395O .
  52. ^ WJ Cocke, MJ Disney, DJ Taylor: Discovery of Optical Signals from Pulsar NP 0532 . In: Nature . tape 221 , no. 5180 , 1969, p. 525-527 , bibcode : 1969Natur.221..525C .
  53. ^ G. Fritz, RC Henry , JF Meekins, TA Chubb, H. Friedmann: X-ray Pulsar in the Crab Nebula . In: Science . tape 164 , no. 3880 , 1969, p. 709-712 , bibcode : 1969Sci ... 164..709F .
  54. ^ YJ Du, GJ Qiao, W. Wang: Radio-to-TeV Phase-resolved Emission from the Crab Pulsar: The Annular Gap Model . In: Astrophysical Journal . tape 748 , no. 2 , 2012, p. 1–12 , bibcode : 2012ApJ ... 748 ... 84D .
  55. ↑ IR Linscott, TH Hankins: High Frequency Observations of Giant Pulses from the Crab Pulsar . In: Bulletin of the American Astronomical Society . tape 12 , 1980, pp. 820 , bibcode : 1980BAAS ... 12..820L .
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  88. ↑ "Beautiful Minds: Jocelyn Bell Burnell", BBC television documentary broadcast April 7, 2010
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