Article Posted on : - Oct 27, 2013

Artistic impression of the planetary system around the Sun-like star HD 10180. An ESO photo

LONDON (PTI): Astronomers have discovered one of the richest planetary systems - containing up to seven planets orbiting a Sun-like star - 127 light years from Earth.

Using The European Southern Observatory (ESO)'s HARPS instrument scientists detected a solar system containing at least five planets, around the star HD 10180.

The researchers also have tantalising evidence that two other planets may be present, one of which would have the lowest mass ever found.

This would make the system similar to our Solar System in terms of the number of planets, researchers said.

The team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System.

"We have found what is most likely the system with the most planets yet discovered," said Christophe Lovis, lead author of the study.

"Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system," said Lovis.

Astronomers used the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla, Chile, for a six-year-long study of HD 10180, located 127 light-years away in the southern constellation of Hydrus.

They detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets.

The five strongest signals correspond to planets with Neptune-like masses - between 13 and 25 Earth masses - which orbit the star with periods ranging from about 6 to 600 days.

These planets are located between 0.06 and 1.4 times the Earth-Sun distance from their central star.

"We also have good reasons to believe that two other planets are present," said Lovis.

One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of the Earth.

It is very close to its host star, at just 2 per cent of the Earth-Sun distance. One "year" on this planet would last only 1.18 Earth-days, researchers said.