PSR B1919+21 is a pulsar with a period of 1.337 seconds and a pulse width of 0.04 second. It is notable for being the first radio pulsar ever discovered (in July 1967 by Jocelyn Bell Burnell). Its original designation was CP 1919 and it is also known as PSR J1921+2153. It is located in the constellation of Vulpecula.
Before the nature of the signal was determined, the researchers, Bell and her Ph.D supervisor Anthony 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?[3]
The observation was given the half-humorous designation Little green men 1, until researchers Thomas Gold and Fred Hoyle correctly identified these signals as rapidly rotating neutron stars with strong magnetic fields.
When Hewish and Martin Ryle received the Nobel Prize in physics in 1974 for their work in radio-astronomy and pulsars, it was argued by Hoyle that Burnell should have been a co-recipient of the prize.
^S. Jocelyn Bell Burnell (1977). "Little Green Men, White Dwarfs or Pulsars?". Cosmic Search Magazine. Retrieved on 2008-01-30. (after-dinner speech with the title of Petit Four given at the Eighth Texas Symposium on Relativistic Astrophysics; first published in Annals of the New York Academy of Science, vol. 302, pages 685-689, Dec., 1977)