ST. PETERSBURG, September 24. /ITAR-TASS/. St. Petersburg astronomers have spotted one more planet circling a star in the Alpha Centauri system just 4.36 light-years away from the Solar System. The discovery was announced on Wednesday at a scientific conference Journees-2014 held at the Pulkovo Observatory in St. Petersburg.

The new plant cannot be seen even though a telescope - astronomers calculated its approximate location by mathematical methods. It is located outside the so-called habitable zone, or the orbital region around a star in which an Earth-like planet can possess liquid water on its surface and possibly support life.

“We believe that this planet may be located at a distance of 80 astronomical units /a unit of length, roughly the distance from the Earth to the Sun, which is 150 million kilometers/ and is orbiting around the centre of the binary star system Alpha Centauri AB with an orbital period of about 100 years,” Ivan Shevchenko, the head of the laboratory of planets and small bodies dynamics at the Pulkovo Observatory, told ITAR-TASS.

It is a second known planet in the Alpha Centauri system. The first one was found in 2012 near Alpha Centauri B by the Harps instrument at the European Southern Observatory's La Silla facility in Chile. As of now, astronomers have discovered 1,791 exoplanets in 110 planetary systems outside our Solar System.

Most of exoplanets were detected by the so-called transit method, which is based on the observation of a star's small drop in brightness, that occurs when the orbit of one of the star's planets passes /”transits”/ in front of the star, Shevchenko said, adding that this method was suggested by Otto Struve /1897-1963/, one of the most outstanding astronomers of the 20th century.

Along with the transit method, there are other techniques that are traditionally used to detect extrasolar planets, including the radial velocity method and the astrometry method. The latter was first used by famous French mathematician Urbain Le Verrier, who is known for his prediction of the existence of the then unknown planet Neptune in 1846.