Astronomers spot orbiting companion around dying star for first time
Researchers have directly observed a close-orbiting companion star around an aging giant star—a phenomenon never before captured on camera. The discovery reveals gaps in current models of stellar physics and demonstrates how advanced radio imaging can detect binary systems, opening new ways to understand how stars evolve and influence one another.
Originaltitel: Evidence for the Keplerian orbit of a close companion around a giant star
<p>Close companions influence stellar evolution through tidal interactions, mass transfer and mass-loss effects. While such companions are detected around young stellar objects, main-sequence stars, red giants and compact objects, direct observational evidence of close-in companions around asymptotic giant branch (AGB) stars has remained elusive. Here we present (sub)millimetre time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB star π<sup>1</sup> Gruis. The companion, slightly more massive than the AGB star, is likely a main-sequence star. Unlike more evolved stars with companions at comparable distances, the companion of π<sup>1</sup> Gruis follows a circular orbit, suggesting an eccentricity-generating mechanism during the late- or post-AGB phase. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimetre interferometry in detecting the Keplerian motion of close companions to giant stars and open avenues for our understanding of tidal interaction physics and binary evolution.</p>