An international team of astrophysicists led by Jorge Lilo-Box and David Barrado at the German-Spanish Astronomical Center at Calar Alto in southern Spain used computer simulation to analyze data from NASA's Kepler space telescope to discover the alien world.
Their findings were published in December and have now been accepted in the journal Astronomy and Astrophysics Letters.
The Kepler satellite telescope is designed to find Earth-like planets orbiting distant stars. It detects eclipses – changes in the brightness of starlight caused by planets passing in front them.
In the case of the red giant star KIC 8219268, some 6.3 times bigger than the Sun, it was observed that a reduction in luminosity occurred every 6.24658 days.
At first it was thought that the reduction was a 'false positive', caused by light curve variations. Further investigations into the distortions of the star's shape caused by the gravity of a passing object confirmed the presence of a planet, which was named Kepler-91b.
It is only the 16th exoplanet to be confirmed by this method, of more than 1,800 exoplanets discovered so far in total.
Despite being 35 percent bigger than Jupiter, the biggest star in our solar system, Kepler 91-b has 14 percent less mass, making it less than half as dense as water.
The unlucky planet is constantly blasted by radiation from the nearby red giant. It is in the final stages of its life and will be swallowed by its mother star in approximately 55 million years.