Lost letters' Neptune revelations

Lost letters' Neptune revelations

By Christine McGourty
BBC science correspondent in Dublin

Long-lost documents relating to the 19th Century discovery of the planet Neptune are shedding new light on one of the most controversial episodes in the history of astronomy.

British Neptune correspondence went missing from the Royal Greenwich Observatory

Speaking at the UK/Ireland National Astronomy Meeting in Dublin, a historian who has pored over hundreds of letters from the period says British scientists have taken more credit for the discovery than they deserved.

The planet was found on 23 September 1846 after the French astronomer Urbain Jean-Joseph Le Verrier calculated its likely location, based on perturbations in the orbit of Uranus.

He wrote to German astronomers equipped with a powerful telescope, telling them where to look.

The new planet was discovered at the Berlin Observatory immediately.

Not quite sure

But the find was quickly mired in controversy, with Britain's powerful Astronomer Royal, George Airy, arguing that a young Cornish mathematician, John Couch Adams, deserved a large share of the credit, having made similar predictions for the likely location of the missing eighth planet in 1845. It was said his predictions had been ignored.

The exact details of the matter have been difficult to establish because crucial British Neptune correspondence (1837-1848) went missing from the Royal Greenwich Observatory.

The documents were found in 1999 in Chile and are being studied by historian Dr Nicholas Kollerstrom of University College London.

He now says the British claims have been exaggerated.

"The British case was largely constructed after the discovery of the planet and we're now discovering that it gave the Brits a bit too much credit," he says.

"Adams had done some calculations but he was rather unsure about quite where he was saying Neptune was."

The burden of blame has traditionally fallen on Airy for failing to act on the mathematician's predictions. But Kollerstrom argues that Airy was largely responsible for Adams being noticed at all.

Ogre and despot

"In order to construct this British maths hero with his wonderful predictions, Airy took a lot of blame for not having acted," says Kollerstrom. "In reality, a more thorough perusal of the documents shows that Adams was rather uncertain and his predictions ranged over as much as 20 degrees."

He says Adams and Le Verrier were doing very similar calculations, but Adams, who was only in his twenties, never had the confidence to say "look there and you will find it".

"He was rather vague and he was vacillating - his predictions kept changing. And I would suggest that's why the British spent six weeks looking for Neptune and not finding it. In contrast, the Germans found it in half an hour."

He describes what follows as "a remarkable British takeover". "They gave themselves far too much of the credit and Adams ended up with much more than was due to him, even though he had done some remarkable calculations," says Kollerstrom.

"Le Verrier has been almost wiped out by history because the Brits were so successful at taking the credit," he adds. "I think he was personally traumatised by what had happened and he ended up as a complete ogre and despot in his later years. I think he was inwardly shattered by having the credit taken from him."

Kollerstrom's conclusions are likely to be controversial, but historians will be able to consider the material for themselves when the complete Neptune Correspondence is published for the first time at the end of this year.