PSR B1919 + 21

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Chart Showing Radio Signal of First Identified Pulsar.jpg

PSR B1919 + 21 is the first pulsar to be discovered . It has a period of 1.337 s. It is located in the constellation Vulpecula ( little fox) at right ascension 19h19m16s and declination + 21 ° 47 'and is about 2000 light years away from the solar system. It was discovered in 1967.

properties

PSR B1919 + 21 emits radio waves in the frequency range from 85  MHz to 2.7  GHz . The period of the pulsar is 1.337301192269 seconds and increases by 1.34809 · 10 −15 seconds per second. The pulse length measures 0.04 s.

Discovery story

PSR B1919 + 21 was discovered on November 28, 1967 by doctoral student Jocelyn Bell . With her doctoral supervisor Antony Hewish , she investigated scintillations (apparent change in radiation intensity) of radio signals in order to detect quasars . Since quasars are compact radio sources, scintillation is more pronounced with them than with extended objects. Hewish had designed and built a radio telescope at Cambridge University for this purpose . This telescope - it was put into operation in July 1967 - produced about 30 meters of data sheets a day, which Bell evaluated manually. In the summer of 1967 she discovered atypical fluctuations in the recorded radio signals, which Hewish initially considered to be interference from passing cars - any signal reflections from the moon or satellites that could have disrupted the sensitive telescope were also taken into account and examined.

The regularity of the impulses and the short period of a little more than a second seemed to indicate a non-natural cause. Since Hewish and Bell calculated that the source was outside the solar system but still inside the Milky Way , but still assumed that the signals were of artificial origin, they considered the discovery of an extraterrestrial intelligence. They therefore named the signal source internally “LGM-1” ( “Little Green Man 1” , an unofficial name that was still used for the first pulsars), officially it was given the name CP 1919 , which is Cambridge pulsar with α = 19h19m means.

If the signals had actually been sent by aliens, they would have had to show a spectral shift according to the Doppler effect , since the alien planet would have had to move around a star like the earth . However, no Doppler effect could be detected, so the extraterrestrial source could be excluded. When Hewish published the results so far in February 1968, it was still not clear which object was emitting the radio pulses. Ultimately, the astronomers Franco Pacini and Thomas Gold theoretically demonstrated that the pulsar is a neutron star - an object that has only been known hypothetically since 1934.

Nobel Prize Award

For the discovery of the pulsar, Antony Hewish received the 1974 Nobel Prize in Physics. Jocelyn Bell was not included in the award ceremony - a decision that was quite controversial at the time.

Cultural processing

The British post-punk band Joy Division used an image of the radio pulses from this pulsar as the cover for their debut album Unknown Pleasures in 1979. The image was taken for the cover of the Cambridge Encyclopedia of Astronomy, which they in turn derived from the doctoral thesis of Harold Craft Jr . reprinted from 1970.

literature

  • Ralf Berhorst: The pulse of the neutron star in: GEO compact No. 6 - Das Universum, p. 101f., Verlag Gruner & Jahr, 2006
  • A. Hewish, SJ Bell, JDH Pilkington, PF Scott, and RA Collins. Observation of a rapidly pulsating radio source. in: Nature 217: 709-713, 1968
  • Moffet, AT, and Ekers, RD, Detection of the pulsed radio source CP1919 at 13 cm wavelength , in: Nature, 218, p. 227, (1968)

Web links

Remarks

  1. ↑ Timothy Rankins, Joanna Rankin: Arecibo Multi-Frequency Time-Aligned Pulsar Average Profile and Polarization Database (PDF; 9.2 MB), P. 3
  2. ↑ Stephen Hawking noted, “I remember that in the seminar in which they announced their discovery they [refer to Bell & Hewish] called the first sources they found LGM 1-4 - LGM for “Little Green Men” ”cf. Stephen Hawking: A Brief History of Time, dtv: 2001, p. 125
  3. ↑ Unknown Pleasures . Joy Division. June 1979. Retrieved June 11, 2009.
  4. ↑ Harold D. Craft, Jr: Radio Observations of the Pulse Profiles and Dispersion Measures of Twelve Pulsars (September 1970). PhD Dissertation Online Catalog from Cornell University