Tom Wagg was doing work-experience at Keele University, UK, when he spotted the planet two years ago by finding a tiny dip in the light of a star as a planet passed in front of it.
It took two years of further observations to prove that Wagg's discovery really is a planet.
"I'm hugely excited to have a found a new planet, and I'm very impressed that we can find them so far away," said Wagg, now aged 17.
Wagg's planet has been given the catalogue number WASP-142b, being the 142nd discovery by the WASP collaboration. It is in the Southern constellation of Hydra.
The planet is the same size as Jupiter, but orbits its star in only two days. With such a short orbital period the transits occur frequently, making such planets much easier to find.
Wagg, a pupil at Newcastle-under-Lyme School, has always been keen on science and wants to study physics at university.
He asked for the work-experience week after learning that Keele University had a research group studying extra-solar planets.
"Tom is keen to learn about science, so it was easy to train him to look for planets," said Professor Coel Hellier, who leads the WASP project at Keele.
The planet is one of a class of 'hot Jupiter' planets, which - unlike the planets in our own Solar System - have very tight orbits close to their stars.
