In the league table of unsung heroes of science, Stanley Hey, who died earlier this year, must rank near the top. Little known to the outside world-or even to today鈥檚 astronomers-this unassuming physicist made the next three important discoveries in radio astronomy after the initial detection of cosmic radio waves. His story begins in the darkest days of the Second World War, when the ex-crystallographer was plucked from the obscurity of teaching physics at a grammar school in the north of England and set to work as a radar analyst.
AS ANOTHER long winter鈥檚 night was drawing to a close, British radar operators began to relax. It was 27 February 1942. Since the Battle of Britain 18 months earlier, the Luftwaffe had taken to bombing the country at night. The radar teams at anti-aircraft batteries were the country鈥檚 early warning system, and it had been a quiet night on the southern front.
Then the nightmare began. All across southern England, radar screens sprang to life. Not with echoes, but with static that washed out the screens with flickering snow. The radar operators feared the worst: the Nazis had acquired a weapon they dreaded, one that allowed blanket jamming of all Allied radar.
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Nerves were on edge in Whitehall, too. Earlier that month, defence chiefs had been humiliated when Hitler鈥檚 most deadly battle cruisers, Scharnhorst and Gneisenau, had slipped out from the blockade of Brest in north-west France. Under cover of bad weather, they had brazenly sailed up the English Channel to safety in Wilhelmshaven. In the aftermath of this escape, British high command grew worried that the Germans might find a way to jam radar on a massive scale. With Allied radar disabled, the Nazis would be able to move their warships around in any weather, or unleash massive night air attacks on English cities without fear of detection en route. So the Army Operational Research Group appointed a young physicist, Stanley Hey, to coordinate all reports of radar jamming. As Hey later recalled: 鈥淪cientifically, the study of jamming appeared to be a most unattractive proposition, but it was wartime and one had to accept necessary duties however irksome they might seem.鈥�
Just a fortnight later, Hey was propelled to the front of the war effort. His desk was swamped by reports from all over the country of the massive radar jamming on 27 February. From a requisitioned mansion in Richmond in south-west London, Hey began to pin down the location of the Nazis鈥� secret weapon.
A curious pattern emerged. In the morning, the jamming seemed to be coming from the eastern part of occupied France. Around midday, the Nazi鈥檚 jamming device was due south of Britain. By the afternoon it was further west again. Then at sunset the jamming stopped.
Ingenious though Hitler鈥檚 scientists may have been, Hey realised there was a more straightforward explanation for the flurry of snow on radar screens. 鈥淎lmost all the sites found that the source followed the bearing of the Sun throughout the day,鈥� Hey reported. Two of the radar operators also measured the height of the jamming signal, and it too matched the Sun鈥檚 position.
Hey鈥檚 discovery of radio waves from the Sun quieted the beating hearts in Whitehall, but it brought no immediate fame. His finding remained classified until the end of the war, when it was finally published in Nature. 鈥淚 was surprised to find that it was greeted with scepticism in some quarters,鈥� he said later.
Not for the first time in science, the acknowledged experts 鈥渒new鈥� too much. In 1901, French physicist Charles Nordmann had laid out an antenna 175 metres long on the flanks of Mont Blanc, with the express purpose of searching for solar radio waves, but he registered none. And in the 1930s, American engineer Karl Jansky detected radio waves from the Milky Way, but failed to pick up any signals from the Sun. So radio physicists were convinced that the Sun wasn鈥檛 a source of radio waves.
Hey鈥檚 own background, on the other hand, was in crystallography, and he didn鈥檛 have any preconceptions about the Sun as a source of radio waves. Hey was generous to his critics and put their scepticism down to the fact that 鈥渢he startling revelation was now coming from an unlikely source: soldier operators on anti-aircraft sites, and an analyser (myself) with practically no previous experience of radio science鈥�.
As a scientist co-opted into the military, Hey also tried to fathom the cause of the great radio outburst. To obtain the Sun鈥檚 precise bearings, he had telephoned the Royal Observatory. During the conversation, he asked if there was anything unusual about the Sun. The astronomer on duty replied that there was a very large sunspot near the centre of the Sun鈥檚 disc, with solar flares erupting all around it.
Sunspots and flares build up and die away in an 11-year cycle. Nordmann and Jansky had had the misfortune to be checking out the Sun during periods of minimum solar activity. Hey had hit a period towards the end of a 鈥渟unspot maximum鈥�, when the Sun鈥檚 magnetic fields were untangling in a series of giant flares.
Meanwhile, Hey was faced with another puzzle. With the advent of the V2 rocket, which Hitler began to launch on London in September 1944, Hey arranged radar sets to look steeply upwards, hoping to detect the incoming rockets. Hey鈥檚 upward-looking radars were a great success. They spotted every rocket that fell in the London area-but they were plagued by strange echoes from some 80 kilometres up, each lasting only a few seconds. Hey guessed he was picking up the trails of meteors as they burnt up in the Earth鈥檚 atmosphere. After the end of hostilities, he set up a radar system specifically to check out these echoes. They did indeed correspond to the showers of meteors that amateur astronomers already knew well. But in addition, Hey discovered daytime meteor showers that can鈥檛 be detected in any other way.
In his attempt to improve the sensitivity of his radars, Hey made a third ground-breaking discovery. He found a small source of radio waves in the constellation of Cygnus. We now know that this object, Cygnus A, is a disc of hot gas circling a supermassive black hole.
After the war, Hey stayed in radio astronomy at the Royal Radar Establishment in Malvern, working in his own quiet and modest way. But he had started something. At Cambridge, a young researcher named Martin Ryle set out to study in detail the radio waves from solar flares, using a double-telescope interferometer: it would eventually lead on to the great radio telescope arrays of today. And at Manchester, another budding scientist borrowed one of Hey鈥檚 radar sets to extend the research on meteors. Bernard Lovell chose a secluded spot for Hey鈥檚 redundant radar, in the university鈥檚 botanic gardens at a place called Jodrell Bank鈥�