The Alpha Centauri (α Cen) system is composed of three stars: 2 Sun-like stars (α Cen A and B) in a binary pair and an M-dwarf (Proxima Cen) that orbits the pair at some distance. At the time of the project, 3 exoplanets had been confirmed around Proxima, though none yet had been detected around the A or B components. Studies suggest that stable orbits exist around either star, including their theoretical habitable zones. Combining this with the fact that they are the closest stars to Earth, as well as potential analogs to our own Solar System, make them appealing targets for exoplanetary investigation.
With this in mind we performed high resolution differential astrometry on the pair, using the GRAVITY instrument operating on the Very Large Telescope Interferometer (VLTI) in Chile, and measuring the minute deviations from their expected orbits that would result from hidden mass within the system, such as a planet orbiting one of the stars. Between the proximity of the α Cen system to our own, combined with the fact that GRAVITY wasn't originally designed to observe this type of object, resulted in us being required to resolve a number of unique challenges in order to properly exploit the data and achieve the precision required to detect exoplanets.
These techniques were also utilised for a number of other binary star systems, with the same goal of detecting exoplanets. The plan was to study a "simpler" system, that is to say one that presented fewer of the challenges we faced with α Cen, which would help us to develop techniques to resolve these various challenges individually rather than trying to solve them all simultaneously.