Undergraduate Kevin Apps, 25, has been credited with the discovery by internationally-renowned "planet hunters" Geoff Marcy and Paul Butler of the Nasa-funded WM Keck Observatory in Hawaii.

Kevin Apps: Suddenly the focus of world attention thanks to his extra-terrestrial discovery

Kevin identified 30 new stars that could have planets - and came up trumps on one of them.

Perhaps the most astonishing aspect of Kevin's find is that until 1996 he worked in a factory making Duracell batteries and only went to university because he was made redundant.

Kevin described to BBC News Online how he e-mailed Marcy and Butler - the most successful planet hunters with nine of the 12 known "extra-solar" planets to their names - to tell them they were looking at the wrong stars.

Star 'wobble'

"In November 1997, I got hold of an astronomical catalogue which lists 118,000 stars and went through it manually," he said.

"When I compared it to the list of 300 that Marcy and Butler were investigating, I realised that 30 stars had been misclassified.

"It was a bit nerve-wracking e-mailing them - they could have said 'mind your own business', but instead they checked it out and found out I was right, so I said, 'Do you want me to choose 30 substitutes?' and they accepted."

Kevin compiled a list of stars based on those most similar to our own sun and e-mailed them to the Keck team.

The Keck Observatory: Can detect when stars 'wobble' (WM Keck Observatory)

On 19 July, the Keck Observatory, which houses the largest telescope in the world, contacted Kevin to tell him they thought they had found a planet orbiting one of his stars and they wanted to credit him.

'Over the moon'

During the next two months, the Keck team measured the "wobble" - caused by the gravitational pull of an orbiting planet - of a star called HD 187123 in the constellation of Cygnus, and confirmed that a new world roughly 200 times larger than Earth had been found, 154 light years away.

Kevin said: "I suppose you could say I was over the moon.

"It's amazing. These guys have been doing this work for 10 years and all I really did was suggest where they should look and I end up getting credited as a co-discoverer."

Kevin has been fascinated by astronomy since he was seven and had originally intended to accept a place at a London university to study the subject after his A-levels, but it proved too expensive.

Instead, he took a job in a Duracell factory in his hometown of Crawley in Surrey, where he worked for six years before being made redundant.

No 'Planet Kevin'

"I had some redundancy money and then my mum died. Since I'd come into a bit of money, I thought I'd go to university," he said.

Groundbreaking: The Keck's image of a meteor striking Jupiter (WM Keck Observatory)

Kevin flew to Hawaii and visited the Keck Observatory before taking up a degree in Physics and Astrophysics at Sussex University in 1997. He is in his second year of the course.

He said the work that led to the discovery had nothing to do with his university course, he just wanted to ensure that the Keck telescope, which costs a dollar a second to run, "wasn't wasting any time looking at the wrong stars".

Despite being credited with its discovery, Kevin doubts the planet will be named after him.

"You just don't get things named after you anymore. There's no real protocol for naming stars, so they'll probably call it HD 187123 'B'," he said.

Kevin's success has earned him an unpaid position as a researcher identifying stars likely to have orbiting planets.

Observatories around the world are currently investigating 300 stars suggested by Kevin.