London: 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.