HAMBURG (dpa) – An international team of astronomers has discovered 11 new planets outside the solar system, raising fresh speculation about the possibility of life in outer space.
Astrophysicists from the Geneva Observatory and the European Southern Observatory (ESO) headquartered in Germany were involved in the detections announced earlier this month.
Since the first extra-solar planet was found orbiting around the star 51 Pegasi in 1995, astronomers have pinpointed between 60 and 70 such heavenly bodies across the universe.
Each discovery raises new questions about the formation and behaviour of planets among scientists raised on the assumption that distant planets orbited stars the way the Earth and other planets in the solar system revolve around the sun.
But astronomers are now detecting planets of unexpected size in areas where they least expected to find them. Last year, they found a handful of new planets similar in size to small stars and others that moved freely in space without orbiting any star.
Some of the 11 planets whose discovery has just been disclosed have special characteristics, according to the ESO.
One of them is a gas giant at least 5.6 times as massive as Jupiter, the largest planet in the solar system. It was detected around a star known under the scientific designation HD28185.
Many of the previously discovered extra-solar planets of similar size were found close to stars or revolved around them in eccentric orbits. But the new one has an almost circular orbit similar to that of our own planet.
Its orbital period of 385 days is also similar to the year taken by the Earth to travel around the sun. Its average distance from its central star is 150.6 million kilometres, almost the same as the 149.6 million kilometres between our planet and the sun.
This would place the new planet in a so-called hospitable zone where temperatures similar to those on Earth are possible.
Although such gas giants are not considered favourable to the development of life forms, they could have moons around them where life might be theoretically possible.
Another new discovery is a two-planet system around the star HD82943 where the orbit of one of the planets is twice as long as that of the other. Such commensurable orbits also exist in the solar system.
A further two-planet system was detected near the star HD74156, with one of the planets similar to the mass of Jupiter and the other having a far greater mass.
Another new discovery was a giant planet 3.4 times the mass of Jupiter that approached to within 5 million kilometres of the star HD80606. At its furthest point it was 127 million kilometres away.
In contrast Mercury, the planet nearest the sun, is 46 million kilometres away at its closest point.
None of the extra-solar planets has been seen with telescopes. They are detected indirectly by the effects of gravity on the motions of their mother star.
Calculations of the changes in motion of these stars allow astronomers to draw conclusions on the orbit of the planets, their mass and their distance from the central stars.
A major problem affecting observation using current telescope technology is that light shining from the stars tends tends drown all weaker sources of light in the vicinity.