It was the discovery that scotched the "little green men" hypothesis.
On a cold night in December 1967 a young postgraduate student from Cambridge University with a radio telescope recorded a series of regular signals from outer space.
The event was significant because it mirrored a recording taken from a different location in the sky the previous month which, it had been suggested, could have been a form of communication from an intelligent extraterrestrial civilisation.
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"It was highly unlikely that there were two lots of little green men on opposite sides of the universe both deciding to signal the rather inconspicuous earth at the same time using a daft technique," Professor Dame Jocelyn Bell Burnell noted years later.
In fact what had been discovered was a pulsar - a rapidly rotating neutron star which was issuing a beam of electromagnetic radiation. The revelation led to a Nobel prize, but not for Dame Jocelyn. Instead, it was her thesis supervisor Antony Hewish who was awarded the Nobel Prize for Physics in 1974.
Although Dame Jocelyn has been circumspect on the matter, saying the Nobel Prize would be demeaned if awarded to research students except in extraordinary circumstances, it is now generally recognised that her head of department won the prize for a discovery that was at least as much hers as his. It is also a compelling metaphor for the inherent sexism that many argue was prevalent in universities in general at the time and physics departments in particular.
Earlier this week, Dame Jocelyn, now a leading astrophysicist and visiting professor of astrophysics at Oxford University, was unveiled as the president elect of the Royal Society of Edinburgh - the first female to hold the post in its 230-year history. And at the time she spoke frankly to The Herald about her experiences in the male-dominated world of academia in the 1960s.
Reading physics at Glasgow University, she found herself as the only female in a class of 50. "When a woman entered the lecture theatre all the guys stamped and whistled and cat-called," she recalled.
"We would call it harassment these days, but it was the tradition. The academic staff knew it was going on and did nothing to stop it."
Dame Jocelyn also spoke of the difficulties she encountered in the 1950s studying science at secondary school in County Armagh, Northern Ireland, where she was born. "In the first week a message went round that the girls should go to one room and the boys to another. They had sent the boys to the science lab and the girls to the domestic science room."
While society has changed a great deal since then, those experiences are just as relevant today. The reason Dame Jocelyn was able to study science at school was because her parents complained, and she believes to this day that advice from family is the most powerful influence on the choices pupils make - but is still often far behind the times.
"You can convert the teachers and you can convert the kids, but if they go home saying they want to be a physicist and the parents question why, then it makes it very difficult," she said.