A Sun-like star orbiting a boson star

The high-precision astrometric mission GAIA recently reported the remarkable discovery of a Sun-like star closely orbiting a dark object with a semimajor axis and period of 1.4 au and 187.8 d, respectively. While the plausible expectation for the central dark object is a black hole, the evolutionary mechanism leading to the formation of such a two-body system is highly challenging. Here, we challenge the scenario of a central black hole and show that the observed orbital dynamics can be explained under fairly general assumptions if the central dark object is a stable clump of bosonic particles of spin-0 or spin-1, known as a boson star. Aside from possible formation mechanisms leading to a star orbiting a boson star, we show that the theory space of boson stars allows for a fairly natural mimicker of binary observations such as the recent one by GAIA. We further explain how future astrometric measurements of similar systems will provide an exciting opportunity to probe the fundamental nature of compact objects and test compact alternatives to black holes.