PSR B1919+21

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″
Characteristics
Evolutionary stage	Pulsar
Astrometry
Distance	2283.12 ly
Details
Mass	~1.4 M☉
Radius	~1.4 × 10−6 R☉
Luminosity	0.006 L☉
Rotation	1.3373
Age	16 Myr
Other designations
PSR J1921+2153, PSR 1921+2153, PSR B1919+21, PSR 1919+21, WSTB 12W15, PULS CP 1919+21, PULS CP 1919, CP 1919+21, CP 1919

PSR B1919+21 is a pulsar with a period of 1.3373 seconds, and a pulse width of 0.04 second. It was the first radio pulsar discovered (on November 28, 1967 by Jocelyn Bell Burnell and Antony Hewish). 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 R.A. 19^h 19^m. It is also known as PSR J1921+2153 and is located in the constellation of Vulpecula.

Discovery

In 1967, a radio signal was detected using the Interplanetary Scintillation Array of the UK Mullard Radio Astronomy Observatory by Jocelyn Bell and Antony Hewish. The signal had a 1.337302088331 second period and 0.04 second pulsewidth. It originated at celestial coordinates 19^h 19^m 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 CP1919, 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 Ph.D supervisor Antony Hewish, somewhat seriously considered the possibility of extraterrestrial life:

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

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.

Cultural reference

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.