LGM-1, 'Little Green Men'
A radio signal ticked too regularly to seem natural, so its discoverers jokingly named it 'Little Green Men'.
What was reported
In 1967 Jocelyn Bell, a PhD student at Cambridge, was checking long paper charts from a new radio telescope when she noticed a small patch of 'scruff' that kept coming back. On 28 November a faster recording showed it was a series of sharp pulses, exactly 1.337 seconds apart.
The pulses were so regular that the team briefly wondered whether they were artificial and nicknamed the source LGM-1, for Little Green Men. Then Bell found a second source in another part of the sky.
Explanations offered
The signals came from a pulsar: a rapidly spinning neutron star, the collapsed core of a massive star, sweeping beams of radio waves past Earth like a lighthouse. It was the first ever found, now known as PSR B1919+21. Hewish shared the 1974 Nobel Prize in Physics for the work; Bell's exclusion became a famous example of a discovery going unrecognised.
- When
- 28 November 1967
- Where
- Mullard Radio Astronomy Observatory, Cambridgeshire, England
- Witnesses
- Jocelyn Bell and Antony Hewish
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.