Astronomers were beaten to the discovery of pulsars by an American airman scanning the skies for Russian missiles, a fascinating new report reveals.

UK scientists Jocelyn Bell Burnell and her supervisor Antony Hewish were credited with finding the first of these rapidly rotating neutron stars in 1967. They are the most accurate clocks in the universe.

The objects emited radio signals so precisely, like a souped-up lighthouse, that astronomers first wondered if they were messages from aliens.

Now a retired US Air Force staff sergeant who was on the front line in the Cold War has come forward to reveal that he detected signals from a number of pulsars several months earlier.

Nature reports online this week that Charles Schisler was based at a remote outpost in Alaska where he operated military radar and identified around a dozen radio sources.

Schisler, now 81, kept a meticulous record of his observations but was unable to speak to anyone about them before because the information was classified.

Astronomers have now checked them and believe that he recorded a pulsar at the heart of the Crab Nebula months before Nature reported the discovery of this new class of object in 1968.

Schisler says he first noticed a faint blip on his radar as he used the Ballistic Missile Early Warning System to watch the skies over Siberia for any signs of an attack.

He noted the signals repeatedly after that and soon realised that they were happening four minutes earlier every day. This told him they must be extra-terrestrial because the star rose four minutes earlier every day due to the Earth’s motion around the Sun.

Schisler drove to the University of Alaska at Fairbanks to meet an astronomy professor who identified the source of his blips as the Crab, the tattered remains of a supernova blast, 6,300 light-years away.

Over the following months, Schisler recorded more celestial radio signals and believes most were pulsars. However, he did not appreciate how special his observations were until he heard of the UK astronomers’ discovery on his short-wave radio. Hewish later won the Nobel Prize for the find while his research student Bell Burnell, controversially, did not.

Nature reports that Schisler regrets being unable to share his own findings more widely. He told them: “I wish we had had a way to communicate with the scientific community.”

Picture: The Crab Nebula, photographed by the Hubble space telescope. (Nasa/ESA).

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