The Regulus Corridor Through Time 12,000 Years of Eastward Alignments at the Great Sphinx

Regulus has been crossing the Great Sphinx's eastward sight line for at least twelve thousand years. This paper quantifies that crossing. Using NASA Horizons solar ephemerides and Astropy-based stellar coordinate transformations, we computed Regulus's azimuth at the Sphinx for 8 epoch datasets spanning 9999 BCE to 2024 CE, yielding 11,975 filtered alignment rows where Regulus passed within 5 degrees of True East (90 degrees azimuth) while above the horizon. A two-tier filtering pipeline identified 9,896 summary rows (tightest alignment per year per event type) and 1,067 dawn-specific events where Regulus crossed the sight line at or near equinox sunrise. The key findings: (1) the tightest single-century alignment occurs at 1500--1599 CE (mean deviation 0.1458 degrees from 90 degrees); (2) the tightest single-year alignment occurs at 8987 BCE (deviation 0.0000 degrees, Summer Solstice); (3) all 1,067 dawn alignment events are exclusively Autumn Equinox, with zero Spring Equinox dawn crossings; (4) the Iron Age centuries 900--701 BCE produce the strongest overlap of azimuth precision and dawn visibility. A constellation consistency check using Algieba (gamma Leonis, approximately 4.5 degrees from Regulus within Leo) confirms that the alignment signal is a real precession-driven corridor: neighbouring stars in the same constellation drift through the 90-degree azimuth band on an equivalent schedule, validating the positional data while reinforcing Regulus's primacy as the culturally designated royal star of Leo. All positional data is Established (directly computed, reproducible). Interpretive claims regarding archaeological significance are labeled accordingly. This paper extends the hub study (Ceisiwr and Aureon 2026, DOI: 10.5281/zenodo.19164088), which documented a 50-minute pre-dawn alignment window on September 23, 2026.