Scientists discover richest planetary system yet

Astronomers have discovered the richest planetary system yet. The system, which is about 127 light years from the Earth, is similar to our solar system in many ways.

Astronomers have discovered a planetary system containing at least five planets and which orbit a Sun-like star, HD 10180.

They said there was evidence of two more planets in the same system, which would make it similar to our solar system in terms of the number of planets and their arrangement.

"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."

The planets and their sun-like star are about 127 light years from Earth, astronomers with the European Southern Observatory said. The system is one of only 15 known to have more than three worlds.

The five planets circle their parent star in a regular pattern like the planets of our solar system, only in a more compact arrangement, the researchers said.

The confirmation of the extra planets would make it the highest tally of alien worlds ever spotted around a single star.

Of the two potential additional planets that may be present, one may have a mass that is the closest to Earth's, if it is confirmed, they added.

Dr Lovis added: ''We also have good reasons to believe that two other planets are present. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2,200 days. The other would be the least massive exoplanet ever discovered, with a mass of about 1.4 times that of Earth.

''It is very close to its host star, at just 2 percent of the Earth-sun distance. One 'year' on this planet would last only 1.18 Earth days.''

The planet would be rocky, like Earth, but probably far too hot to sustain life.

With at least five Neptune-sized planets circling inside an orbit equivalent to that of Mars, the HD 10180 system has a more populated inner region than our solar system.

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.

"This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. 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," he said.

Among the other two planets that could exist, 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 Earth.

So far, astronomers know of 15 systems with at least three planets. The last record-holder was 55 Cancri, which contains five planets, two of them being giant planets.

It took astronomers six years to study it using a planet-finding instrument called the HARPS spectrograph, attached to ESO's 3.6 metre (11.8ft) telescope at La Silla, Chile.