Astronomers spot lightest exoplanet

Astronomers may have discovered the lightest exoplanet ever seen, which appears just as a dot orbiting a young star.
The newly discovered planet orbits the young star HD 95086 at a distance of around 56 times the distance from the Earth to the Sun, twice the Sun-Neptune distance.
Although nearly a thousand exoplanets have been detected indirectly - most using the radial velocity or transit methods - and many more candidates await confirmation, only a dozen exoplanets have been directly imaged.
ESO's Very Large Telescope captured on camera what is probably the lightest of these objects so far.
"Direct imaging of planets is an extremely challenging technique that requires the most advanced instruments, whether ground-based or in space," says Julien Rameau from Institut de Planetologie et d'Astrophysique de Grenoble, France.

"Only a few planets have been directly observed so far, making every single discovery an important milestone on the road to understanding giant planets and how they form," said Rameau.

The likely planet appears as a faint but clear dot close to the star HD 95086. A later observation also showed that it was slowly moving along with the star across the sky.
This suggests that the object, which has been designated HD 95086 b, is in orbit around the star. Its brightness also indicates that it has a predicted mass of only four to five times that of Jupiter.

The observations were made using infrared light and a technique called differential imaging, which improves the contrast between the planet and dazzling host star.
The star itself is a little more massive than the Sun and is surrounded by a debris disc. These properties allowed astronomers to identify it as an ideal candidate to harbour young massive planets. The whole system lies some 300 light-years away from us.
The youth of this star, just 10 to 17 million years, leads astronomers to believe that this new planet probably formed within the gaseous and dusty disc that surrounds the star.
"Its current location raises questions about its formation process. It either grew by assembling the rocks that form the solid core and then slowly accumulated gas from the environment to form the heavy atmosphere, or started forming from a gaseous clump that arose from gravitational instabilities in the disc," said researcher Anne-Marie Lagrange.

"Interactions between the planet and the disc itself or with other planets may have also moved the planet from where it was born," said Lagrange.