PSR B1919+21

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PSR B1919+21
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Vulpecula
Right ascension 19h 21m 44.79808s
Declination +21° 53′ 01.8288″
Evolutionary stage Pulsar
Distance 2283.12 ly
Mass ~1.4 M
Radius ~1.4 × 10−6 R
Luminosity 0.006[1] L
Rotation 1.3373 s[2]
Age 16[1] Myr
Other designations
PSR J1921+2153, PSR 1921+2153, PSR B1919+21, PSR 1919+21, WSTB 12W15, CP 1919+21, CP 1919, LGM-1

PS B1919+21 is a pulsar with a period of 1.3373 seconds[2] and a pulse width of 0.04 seconds. Discovered by Jocelyn Bell Burnell and Antony Hewish on November 28, 1967, it is the first discovered radio pulsar.[3] The power and regularity of the signals was thought to resemble a beacon, so for a time the source was nicknamed "LGM-1" (for "little green men").

The original designation of this pulsar was CP 1919, which stands for Cambridge Pulsar at RA 19h 19m.[4] It is also known as PSR J1921+2153 and is located in the constellation of Vulpecula.


In 1967, a radio signal was detected using the Interplanetary Scintillation Array of the Mullard Radio Astronomy Observatory in Cambridge, UK, by Jocelyn Bell and Antony Hewish. The signal had a 1.337302088331-second period and 0.04-second pulsewidth.[2] It originated at celestial coordinates 19h 19m right ascension, +21° declination. It was detected by individual observation of miles of graphical data traces. Due to its almost perfect regularity, it was at first assumed to be spurious noise, but this hypothesis was promptly discarded. After that, the discoverers proposed an alternative explanation that the signal might be a beacon or a communication from an intelligent extraterrestrial civilization and named it little green men 1 (LGM-1).

The signal turned out to be radio emissions from the pulsar CP 1919, the first one recognized as such. Bell noted that other scientists could have discovered pulsars before her, but their observations were either ignored or disregarded. Researchers Thomas Gold and Sir Fred Hoyle identified this astronomical object as a rapidly rotating neutron star immediately upon their announcement.

Before the nature of the signal was determined, the researchers, Bell and her PhD supervisor Antony Hewish, somewhat seriously considered the possibility of extraterrestrial life:[5]

We did not really believe that we had picked up signals from another civilization, but obviously 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? Who does one tell first?

Nobel Prize controversy[edit]

When Hewish and Martin Ryle received the Nobel Prize in physics in 1974 for their work in radio astronomy and pulsars, Hoyle argued that Jocelyn Bell Burnell should have been a co-recipient of the prize.[6]

Cultural reference[edit]

The English post-punk band Joy Division used an image of CP 1919's radio pulses on the cover of their 1979 debut album, Unknown Pleasures.[7][8][9]


  1. ^ a b "The ATNF Pulsar Catalogue". Retrieved 2010-02-11. 
  2. ^ a b c Arzoumanian, Z.; Nice, D. J.; Taylor, J. H.; Thorsett, S. E. (1994). "Timing behavior of 96 radio pulsars". Astrophysical Journal. 422 (2): 671. Bibcode:1994ApJ...422..671A. doi:10.1086/173760. 
  3. ^ "Pulsar is 1st observed, November 28, 1967". EDN Network. Retrieved 2013-12-20. 
  4. ^ Basu, Baidyanath. An Introduction to Astrophysics. 
  5. ^ Burnell, S. Jocelyn Bell (2004-09-21) [1977]. "Little Green Men, White Dwarfs or Pulsars?". Cosmic Search Magazine. Retrieved 2013-07-28.  (after-dinner speech given at the Eighth Texas Symposium on Relativistic Astrophysics; first published in "Petit Four". Annals of the New York Academy of Sciences. 302: 685–9. 1977. doi:10.1111/j.1749-6632.1977.tb37085.x. )
  6. ^ Judson, Horace Freeland (2003-10-20). "No Nobel Prize for whining". The New York Times. 
  7. ^ Capriola, Adam (2011-05-19). "The History of Joy Division's "Unknown Pleasures" Album Art". Retrieved 2013-06-28. 
  8. ^ "Unknown Pleasures". Joy Division. June 1979. Retrieved 2008-07-05. 
  9. ^ Christiansen, Jen (2015-02-18). "Pop Culture Pulsar: Origin Story of Joy Division's Unknown Pleasures Album Cover". Scientific American. Retrieved 2015-10-04. 

Further reading[edit]

External links[edit]