Tau Volantis was discovered after intense study of the Red Markers, the man-made copies based on the original alien artifact, the Black Marker. The Red Markers, sequestered safely away on distant star systems such as Aegis VII, Aspera and Proxima Centauri, among others, were themselves a mystery, as they were more grown than built. As the Red Markers were studied, it became clear they were receiving the signal they broadcast, rather than creating it themselves.
The Ptolemy Array was built specifically to triangulate the distant signal using three Red Markers. They located the source, and it proved to be the most distant point ever reached by man, Tau Volantis, here in this previously uncharted arm of the galaxy.
This feat of science and technology will hopefully reward mankind with the ultimate prize -- the limitless energy that seems to emanate from the Markers, the source of which we expect to find here.