Astronomers have discovered what they claim is a vast solar system of seven planets, orbiting a sun-like star, 127 light years away from Earth.

An international team has confirmed the presence of the five planets and have tantalising evidence of two more in the planetary system which is believed to be the largest ever detected beyond the sun.

The distance of the planets from their parent star follow a regular pattern, similar to that seen in our own solar system, say the astronomers.

“We have found what is most likely the system with the most planets yet discovered. 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,” Dr Christophe Lovis, who led the European Southern Observatory scientists, was quoted by ‘The Daily Telegraph’.

The parent star, known as HD 10180, lies in the southern constellation of Hydrus 127 light years away. The astronomers patiently studied it for six years using a planet-finding instrument called the HARPS spectrograph, attached to ESO’s 3.6 metre telescope at La Silla, Chile.

From 190 individual HARPS measurements, they were able to detect tiny wobbles in the star’s motion caused by the gravitational tugs of its planets.

The five strongest signals corresponded to planets with Neptune-like masses, between 13 and 25 times that of the Earth. These planets, with orbit periods ranging from six to 600 days, are separated from their star at 0.06 to 1.4 times the distance between the Earth and sun.

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 per cent of the Earth-sun distance. One ‘year’ on this planet would last only 1.18 Earth days.”

The planet would be rocky, like the 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.

So far astronomers have found 15 systems containing at least three planets. The last record holder was 55 Cancri, which has a total of five planets including two gas giants.

The findings have been submitted for publication to the ‘Astronomy and Astrophysics’ journal.

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