Scientists have found a new planetary system with as many as seven planets orbiting a sun-like star.
If would be the richest system of planets outside our own solar system ever found.

Led by astronomer Christophe Lovis from Geneva University, this remarkable discovery "highlights the fact that we are now entering a new era in exoplanet research, said Lovis.

“This shows that we are able to detect complex systems of small planets, which opens up huge perspectives, as these systems are probably very numerous,” the lead researcher told the agency swissinfo.ch.

The new find consists of at least five planets of the same mass as Neptune – 13 to 15 times that of the Earth - orbiting a star called HD 10180, located in the constellation of Hydrus.

The objects take between six and 600 days to orbit their star at distances varying from 0.06 to 1.4 times the distance between the Earth and the Sun - an average of 149 million kilometres, known as one astronomical unit.

"They are made essentially of rocks and ice. They have a solid core. But on top of that is a layer of gas, of hydrogen and helium most likely," said Lovis. "They are probably not habitable."

The astronomers also have “good reasons” to believe that there are two more planets in the same system.
The sixth is thought to resemble Saturn and orbits the star in 2,200 days, while the seventh would be the smallest exoplanet ever discovered, with a mass only 1.4 times that of the Earth.

But its similarity with our planet ends there, as it is extremely close to its star – just two per cent of one astronomical unit; one "year" on this planet would only take just over a day.

“Five are certain and for the other two, whose signal is very small, we are 99 per cent sure,” said Lovis.

Unique find

At up to seven planets, the new discovery nearly matches our own solar system, which has eight. The discovery was unique in several respects, the research team said.

With at least five "Neptune-like planets" orbiting within a distance equivalent to that of Mars, the HD 10180 had a more populated inner region than our own solar system. And all the planets seem to have almost circular orbits.

Using the new discovery as well as data for other planetary systems, the astronomers discovered an equivalent of the “Titius-Bode” law that exists in our solar system: a regular, hidden pattern in the spacing of the orbits of the planets.

“This could be a signature of the formation process of these planetary systems,” said Swiss astronomer Michel Mayor.

Swissinfo.ch