This answer to Has great eyesight been necessary for astronomers? mentions Astronomer Jocelyn Bell Burnell's recounting of a likely first visual observation of a pulsar. This can be found for example in Nature's Air force had early warning of pulsars

Wikipedia's Crab Pulsar includes this passage:

Jocelyn Bell Burnell, who co-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.

Question: What might "scintillation" be in this context, and are "qualified pilots" generally aware of it?


"Scintillation" is the flickering of starlight due to the turbulence in the Earth's atmosphere through which the light passes. It is also known as stars "twinkling."

The current version of the PHAK discusses a number of nighttime optical illusions, but not scintillation. It does discuss, however, autokinesis, which is a less well-known but similar illusion. I don't think it would be outrageous for a pilot who knows about scintillation to connect the two. After all, a pilot can discern the difference between a ground-based light source and a star because the star will scintillate and the ground-based light source will not. Maybe the PHAK should include it, given its interest in identifying false horizons created by lines of ground lights.

Someone knowledgable who observed the visual flicker of the Crab Pulsar would be able to easily tell that it wasn't scintillating because scintillation is random, whereas pulsar flickers are more precisely timed than atomic clocks.

  • $\begingroup$ Thanks for the speedy answer! I've now referenced this here. $\endgroup$
    – uhoh
    Jan 1 '20 at 23:10
  • 2
    $\begingroup$ Ground-based lights can flicker/twinkle too due to smog, fog, etc. $\endgroup$
    – StephenS
    Jan 1 '20 at 23:17
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    $\begingroup$ It would have been a well known phenomenon in the 1950's because star based navigation was very common, even for pilots, and "competent" pilots would have been trained in that regard. $\endgroup$
    – Ron Beyer
    Jan 1 '20 at 23:24
  • $\begingroup$ I wonder if when Jane Taylor wrote the lullaby around 1806 she originally had it "Scintillate, scintillate little star..." then said, "Nah, that won't work! Too many syllables!", tore it up and started over. $\endgroup$
    – John K
    Jan 2 '20 at 2:43
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    $\begingroup$ @StephenS: Or even if they're a long ways away, especially if you're flying in clear desert air fairly early at night, where there's a lot of differential heating of the ground, and air currents &c. Indeed, you can get "twinkle" mirage effects in the daytime. $\endgroup$
    – jamesqf
    Jan 2 '20 at 6:01

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