This week’s photo shows the unique star system HIP 81208, taken by ESO’s Very Large Telescope (VLT) in Chile. Astronomers believe that HIP 81208 is a system consisting of a giant central star (A, the central bright spot), a brown dwarf (B) orbiting it, and a low-mass star (C) in a more distant orbit. However, a new study has revealed a never-before-seen hidden gem: an object (Cb), about 15 times more massive than Jupiter, orbiting the smaller of the two stars (C). The discovery of Cb means that HIP 81208 is a particularly intriguing system with two stars and two smaller objects orbiting each star –– in other words, a quaternary system. The mass of newly discovered object Cb puts it right on the boundary between planets and brown dwarfs – failed stars that are not massive and hot enough to fuse hydrogen into helium. The hidden giant Cb was discovered when a team of astronomers, led by A. Chomez of the Paris Observatory, reanalyzed archival data from the high-contrast Exoplanet Research instrument Spectro -Polarimetric (SPHERE) installed on VLT.

While many other tools use indirect methods to search for distant worlds, SPHERE uses a technique called direct imaging: what we see here is an actual image of the system. Indeed, this is the first hierarchical four-level system discovered through direct imaging, which will prove invaluable in understanding how complex systems like this form and evolve.

Source: ESO/A. Chomez et al.