Sigma Octanus IV artifact
From Halopedia, the Halo wiki
The Sigma Octanus IV Artifact, is a Forerunner artifact first identified as such when it was on display in a museum located on Sigma Octanus IV. It was theorized to have arrived via a comet a long time ago. It was found by the Covenant, who attempted to seize it for themselves; however, the Spartans shut down the Covenant operation and took the scans of the artifact. These scans were theorized to be a star chart of some kind, and the theory was proven to be correct by Cortana and Dr. Halsey. One set of symbols were coordinates to the system where Installation 04 was located and the other one had coordinates to Reach. In Halo:CE and Halo:The Flood, the "blind jump" Cortana made was not so blind. She used the coordinates on the Artifact.