Kevin Apps, a 25-year-old undergraduate at Sussex University, told the Nasa (National Aeronautics and Space Administration) team working with the giant Keck telescope in Hawaii that it was wasting its time looking at certain stars and should concentrate its efforts on another set of stars.
"I checked the stars against a catalogue I got on a CD-Rom from the European Space Agency and found they were not suitable for a planet search," he said. "The guys in America just hadn't noticed themselves because they were too busy perfecting their techniques."
Mr Apps, who is taking a degree in astrophysics, drew up a shortlist of the 30 stars most likely to possess planetary systems, one of which did.
"I checked the colour of the stars to see if they were a similar temperature and brightness to the Sun. I then worked out the composition to see if they had the right elements. It took some time but it paid off," Mr Apps said.
The American team offered to check his shortlist with the Keck telescope. "It's the world's largest telescope and very few professionals get to use it. So for an amateur like me to get his stars on it is amazing. I was over the moon," Mr Apps said.
Geoffrey Marcy, professor of science at San Francisco University, and Paul Butler, an astronomer at the Anglo-American Observatory, said they could not have made the discovery without Mr Apps's help.
"He shows a fierce interest in this research. It's great to have him as a colleague," Professor Marcy said.
The US team also found a second new planet orbiting another star, which brings the total number of planets found outside our solar system to 12. The research is published under joint names with Mr Apps.
The two latest planets were detected by monitoring the gravitational "wobble" exerted on their stars. Neither is likely to support life, as they pass too close to their suns.
But Professor Marcy said the search is likely to discover contenders for extraterrestrial life: "Make no mistake about it, what we're all about is discovering planets where evolution might have gained a toehold."Reuse content