Cosmic findings

Lightest exoplanet ever found imaged by Chilean telescope

Nine years after the Atacama-based VLT imaged the first planet outside of our solar system, the telescope has discovered the lightest of these objects ever found.

Thursday, July 25, 2013  


Ground based astronomy in Chile has contributed yet further information vital in our understanding of the formation and evolution of planets.

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), a team of scientists were able to image the lightest “exoplanet(a planet beyond our solar system) found so far. While almost a thousand exoplanets have been discovered via radial velocity methods (observing disturbances in the orbit of or the light emitted from a star), only a dozen have ever been directly imaged.

Head of the study Julien Rameau of the Institut de Planetologie et d'Astrophysique de Grenoble in France, explained that the incredible power of the VLT in Chile’s northern desert was essential to making this groundbreaking discovery.

“Direct imaging of planets is an extremely challenging technique that requires the most advanced instruments, whether ground-based or in space,” Rameau said. “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.”

The planet — named HD 95086 b — can be seen as a faint dot orbiting its host star. Measurements of the the planet’s brightness indicate that it is four or five times the size of Jupiter — enormous in the context of our solar system, but small enough to require unrivalled technological sensitivity to detect it.

At 10-17 million years old, the host star is young by cosmological standards, and astronomers believe that the planet may have formed within the gaseous and dusty disc that surrounds the star.

“Its current location raises questions about its formation process,” team member Anne-Marie Lagrange, said. “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. Interactions between the planet and the disc itself or with other planets may have also moved the planet from where it was born.”

The star system’s environment seems to be conducive to the existence of water — essential for life as we know it — and astronomers will be keeping a close eye out for other planets within the star’s orbit.

“The brightness of the star gives HD 95086 b an estimated surface temperature of about 700 degrees Celsius,” team member Gaël Chauvin, said. “This is cool enough for water vapour and possibly methane to exist in its atmosphere. It will be a great object to study with the forthcoming SPHERE instrument on the VLT. Maybe it can also reveal inner planets in the system — if they exist.”

Due to its almost non-existent humidity and clear skies, the Atacama is the world’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds in the next decade.