History
The modern history of the Crab Pulsar begins with the identification of the central star of the nebula in optical light. Attention was focused on two stars near the center of the nebula (referred to in the literature as the "north following" and "south preceding" stars). In September 1942, Walter Baade ruled out the ""north following" star, but found the evidence inconclusive for the "south preceding" star. Rudolf Minkowski, in the same issue of Astrophysical Journal as Baade, advanced spectral arguments claiming that the "evidence admits, but does not prove, the conclusion that the south preceding star is the central star of the nebula".
In late 1968, David H. Staelin and Edward C. Reifenstein III reported the discovery of two pulsating radio sources "near the crab nebula that could be coincident with it" using the 300-foot Green Bank radio antenna. They were given the designations NP 0527 and NP 0532. The period and location of the Crab Nebula pulsar NP 0532 was discovered by Richard Lovelace and collaborators November 10, 1968 at the Arecibo radio observatory.
A subsequent study by them including William D. Brundage also found that the NP 0532 source is located at the Crab Nebula. A radio source was also reported coincident with the crab nebula in late 1968 by L. I. Matveenko in Soviet Astronomy.
Optical pulsations were reported by Nather, Warner, and Macfarlane in February 1969.
Jocelyn Bell Burnell, who discovered the first pulsar PSR B1919+21 in 1967, relates that in the late 1950s a woman viewed the Crab Nebula source at the University of Chicago's telescope, then open to the public, and noted that it appeared to be flashing. The astronomer she spoke to, Elliot Moore, disregarded the effect as scintillation, despite the woman's protestation that as a qualified pilot she understood scintillation and this was something else. Bell Burnell notes that the 30 Hz frequency of the Crab Nebula optical pulsar is difficult for many people to see.
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