In the 1800s, F. W. Bessel observed tiny variations in the proper motion of Sirius and Procyon, and attributed it to orbits around a barycenter with other heavenly objects. Those orbits, visible from our planet Earth, support Galileo Galilei's measurements of the angular size of fixed stars, that the largest stars (as seen from our vantage point) are in the arc seconds, and their distance as close as hundreds of astronomical units (AU). The close distance to Sirius for example, is why its 6.5 arc second orbit around the barycenter of its solar system, is visible to us from Earth, as F. W. Bessel noted in 1845.

Synapses

Bessel, G. R. (1845). On Variations of the proper motions of the fixed stars. Astronomische Nachrichten, 22(10), 145–160. https://doi.org/10.1002/asna.18450221002