Astronomers re-analyzing archival data from the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), an instrument installed on the European Southern Observatory’s Very Large Telescope (VLT) in Chile, have spotted a hidden planetary-mass object in the HIP 81208 stellar system.
While HIP 81208 was thought to comprise a massive central star (A), a brown dwarf (B) circling around it, and a low-mass star (C) orbiting further away, the new study has revealed a never-before-seen hidden gem – a gas giant approximately 15 times more massive than Jupiter, orbiting around the smaller of the two stars (C).
The discovery of this object, named Cb, means that HIP 81208 is a unique quadruple system with two stars and two smaller bodies orbiting each one. The mass of Cb places it right at the border between planets and brown dwarfs, failed stars that are not massive and hot enough to fuse hydrogen into helium.
The team, led by A. Chomez of the Paris Observatory, discovered Cb using a method known as direct imaging. SPHERE is designed to detect and study new giant exoplanets orbiting nearby stars by directly capturing images of the exoplanets, as though it were taking their photograph.
“While many other instruments use indirect methods to hunt for far-flung worlds, SPHERE uses a technique known as direct imaging: what we see here is an actual image of the system,” ESO wrote in a post.
HIP 81208 is the first hierarchical quadruple system to be found using direct imaging – a finding that astronomers believe will be key to understanding how complex systems like this one form and evolve.