London, April 10 : Scientists have discovered a possible terrestrial-type planet orbiting a star in the constellation of Leo, which might be the smallest planet found till date.

Discovered by Spanish and UCL (University College London) scientists, the new planet lies at a distance of 30 light years from Earth, has a mass five times that of our planet, but could be the smallest found to date.

"This is the fourth super-Earth planet discovered. This planet is the hot twin of the frozen super-Earth (OGLE-2005-BLG-390lb) we discovered by microlensing two years ago," said Dr Jean-Philippe Beaulieu, a visiting astrophysicist at UCL.

Planets with masses of between one and 10 times the Earth are often dubbed super-Earths. In this case, current models predict that the new planet is a rocky type and has a radius some 50 percent larger than the Earth.

The team of astronomers from the Spanish Research Council (CSIC) working with Dr Beaulieu, made the discovery from model predictions of a new exoplanet orbiting a star in the constellation of Leo.

Simulations show that the exoplanet, dubbed GJ 436c, orbits its host star (GJ 436) in only 5.2 Earth days, and is thought to complete a revolution in 4.2 Earth days, compared to the Earth's revolution of 24 hours and full orbit of 365 days.

On Earth, a full day (sunset to sunset) coincides quite closely with the rotation period. On the new planet, these two periods do not coincide, since the orbital translation period and the rotation period are very similar.

For this reason, a full day on the new planet would take four planetary years, or roughly 22 Earth days.

A re-analysis of archival radial velocities also permitted the identification of a signal that perfectly matches the simulations and corresponds to a planet in resonance with the inner one, meaning that for every two orbits of the known planet, the new planet completes one.

According to Ignasi Ribas, lead author of the study from CSIC, "After final confirmation, the new exoplanet will be the smallest found to date."

Because it is the first one to be identified from the perturbations exerted on another planet of the system, the study of the new planet opens a new path that should lead to the discovery of even smaller planets in the near future, with the goal of eventually finding worlds more and more similar to the Earth.

ANI