June 3, 2013
Least Massive Exoplanet Outside The Solar System Observed By ESO Telescope
Lee Rannals for redOrbit.com — Your Universe Online
The team reported in Astrophysical Journal Letters that they imaged a faint object moving near a bright star. The exoplanet has an estimated mass of four to five times that of Jupiter, which could potentially make it the least massive planet to be directly observed outside the Solar System.
“Direct imaging of planets is an extremely challenging technique that requires the most advanced instruments, whether ground-based or in space,” says Julien Rameau of the Institut de Planetologie et d'Astrophysique de Grenoble (IPAG) in 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.”
Nearly a thousand exoplanets have been detected indirectly, but only a dozen have been directly imaged. VLT was the first instrument to capture the first image of an exoplanet circling around the brown dwarf 2M1207.
The new exoplanet, HD95086 b, circles around the star HD 95086. The astronomers believe the exoplanet is in orbit around the star at a distance of around 56 times the distance from the Earth to the Sun, or twice the Sun-Neptune distance.
HD 95086 is a little bigger than the Sun and is surrounded by a debris disc. These properties allow scientists to identify it as an ideal candidate to harbor young massive planets. Because of how young this star is, scientists believe this new planet formed within the gaseous and dusty disc around 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.” explains Anne-Marie Lagrange, another team member. “Interactions between the planet and the disc itself or with other planets may have also moved the planet from where it was born.”
GaÃ«l Chauvin, another team member on the project, said the exoplanet has an estimated surface temperature of nearly 1,300 degrees Fahrenheit.
"This is cool enough for water vapor 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," Chauvin said.
VLT's SPHERE instrument is a second generation adaptive optics instrument that will be installed on the telescope in late 2013. The team used NACO for the current observation, which is an adaptive optics instrument mounted on one of the 8.2-meter Unit Telescopes.