Exploding star hunters make history

By Dr David Whitehouse
BBC News Online science editor

Two British amateur astronomers have found more than 100 exploding stars, or supernovae - more than any other individuals.

Mark Armstrong: "The thrill of discovery"

A supernova explosion is so big it can outshine the galaxy in which it occurs. Scientists use them to learn about the expansion of the Universe.

Until recently finding supernovae was difficult and confined to professionals, who often found them by chance. But all that has changed.

Using sophisticated, computer-controlled telescopes in their gardens, Mark Armstrong and Tom Boles have become the most successful exploding star hunters in history.

Any given night

They may be classed as amateurs but their equipment and expertise is undoubtedly top notch.

Searching for supernovae occupies the two men almost every clear night.

The first UK supernova, found in 1996

For the past few years, they have perfected the technique of automatically taking pictures of numerous distant galaxies to see if any have an exploding star within their midst.

Mark Armstrong has his observatory in Kent. He discovered his first supernova, the first one ever detected from the UK, on 23 October 1996.

He discovered it close to the central bright region of a galaxy called NGC 673.

Technically, it was what astronomers call a Type-1a, and it was caught before it reached its maximum brightness. These supernovae are used to calibrate the expansion of the Universe.

He found his second one in March 1998 but since then, due to experience and new software, his discovery rate has increased and he has now captured almost 50.

Dark skies

Tom Boles moved to dark Suffolk skies to establish his observatory. He has found 53 supernovae, his most recent one was just two nights ago.

"I look at 11,000 galaxies on a regular basis," he told BBC News Online.

Tom Boles observes thousands of galaxies

At the peak time of the year - the long, dark nights of November - he estimates he can survey 210 galaxies an hour for 13 hours using his three telescopes.

Both astronomers gather so many images they rely on Britain's cloudy weather to help them catch up: overcast nights give them the time to sort through all the images they have accumulated.

"You bring up an image of a galaxy and suddenly you see a change," says Tom Boles.

"It's the thrill of discovery. It's a nice feeling when you know you are the only person who knows it's there," adds Mark Armstrong.

Star snap

When Tom Boles started, he estimates that he had to examine about 7,000 galaxies to find one with a supernova in it.

Now, thanks to better equipment and experience he finds an exploding star roughly every 2,800 galaxies scrutinised.

Notching up number 100

Mark Armstrong also uses three telescopes to scan the sky and says that these days he can record more images of distant galaxies in a couple of nights than he did in an entire year when he started.

At their present rate of discovery, the two men will soon reach the 200 supernovae mark, adding considerably to the work of professionals who take a more detailed look at the exploding stars.

Along the way, Mark Armstrong and Tom Bowles will inevitably overlap. The night of 14 September brought good observing conditions and a first.

They independently found a new supernova - the same one.