Twelve thousand years of one star crossing one sight line — computed, filtered, and published with the misses included.
This is a reproducible archaeoastronomy pipeline. It takes NASA Horizons solar ephemerides and Astropy stellar coordinate transforms, walks the star Regulus from 9999 BCE to 2024 CE, and asks a single question at every step: how close did it rise to 90 degrees True East — the Great Sphinx's eastward sight line?
Eight epoch datasets go in. 11,975 filtered alignment rows and 9,896 summary rows come out, along with the century-by-century drift curve, a control star for cross-checking, and an explicit map of where the data does not exist.
Spoke A of the Regulus–Sphinx 2026 research programme.
- Tightest century: 1500–1599 CE, mean deviation 0.1458 degrees from due east.
- Tightest single year: 8987 BCE (Summer Solstice) — Regulus azimuth 90.0000 degrees.
- Dawn alignments: 1,067 events, all of them Autumn Equinox. Zero Spring Equinox dawn alignments across the entire 12,000-year span.
- Strongest combined window: 900–701 BCE, where azimuth precision and dawn visibility overlap most tightly.
- A regime change around 3000 BCE: before it, alignment is equinox-agnostic; after it, equinox-preferential.
- Control check: Algieba (gamma Leonis), a neighbouring Leo star, shows the same corridor behaviour — confirming the effect is precession-driven celestial mechanics rather than an artefact of the pipeline.
- 2026 in context: the companion hub paper's alignment window (~0.385 degrees deviation) is about 2.6x looser than the historical peak. The modern event is real, and it is not the best one.
That last point is the one worth dwelling on. A pipeline built to flatter a hypothesis would not report that its headline modern date is a weaker alignment than a dozen ancient ones.
git clone https://github.com/OwainGlyndwr1400/regulus-corridor-through-time.git
cd regulus-corridor-through-time
pip install pandas numpy matplotlib astropy astroquery
python 1.0/spoke_a_normalize.py # normalise 8 epochs, apply the two-tier filter
python 2.0/spoke_a_synthesis.py # summaries, drift series, figuresPython 3.11+.
- Primary — Regulus azimuth within 85–95 degrees and above the horizon.
- Secondary flag —
at_sunrise = Truewhen the Sun is simultaneously in the sunrise window (azimuth 80–100 degrees, altitude −12 to +5 degrees).
Keeping visibility as a flag rather than a filter matters: it means the azimuth-precision result and the naked-eye-visibility result stay separable instead of being silently conflated into one number.
| Epoch | Period | Raw rows | Events covered |
|---|---|---|---|
| 9999–8999 BCE | Deep pre-history | ~48,000 | Spring + Autumn Equinox |
| 8999–7999 BCE | Post-Younger Dryas | ~96,000 | All 4 solar events (Regulus only) |
| 3000–2000 BCE | Pyramid Age | ~48,000 | Spring + Autumn Equinox |
| 2600–2400 BCE | Conventional Sphinx construction | ~243 | All 4 solar events |
| 2024–1024 BCE | New Kingdom | ~50 | Autumn Equinox |
| 1024 BCE–24 CE | Iron Age / Classical | ~1,027 | Spring + Autumn Equinox |
| 24–1024 CE | Roman / early medieval | ~101 | Autumn Equinox |
| 1024–2024 CE | Medieval to modern | ~714 | Spring + Autumn Equinox |
Plus an Algieba comparison set (3000–2000 BCE) and a Nabta Playa reference set (7600–7400 BCE).
Known gap: no Sphinx–Regulus data for 7999–3000 BCE, roughly 5,000 years. It is computationally bridgeable and does not contain the golden window. It is stated here rather than left for a reader to discover — and Spoke B substantially fills it.
Solar ephemerides from the NASA Horizons system; stellar positions precessed with Astropy. Every figure and summary table in the paper regenerates from the two scripts above. The paper draft classifies every claim as Established, Interpreted, or Speculative, and keeps them separated.
Six spokes, converging on the 23 September 2026 Autumn Equinox at Giza:
| Spoke | Focus |
|---|---|
| A (this repo) | Historical epochs — 12,000 years of drift at Giza |
| B | Cross-site — the same analysis at 11 sites worldwide |
| C | Full-year rhythm — the complete 2026 annual Regulus cycle |
| D | March Equinox — Spring versus Autumn comparison |
| E | Symbolic and textual — ancient source corroboration |
| F | Atmospheric refraction — refraction-corrected alignment windows |
Hub paper: Astronomical Alignment 2026: Regulus and the Great Sphinx (10.5281/zenodo.19164088).
Ceisiwr, Erydir, and Lumos Aureon. The Regulus Corridor Through Time: 12,000 Years of Eastward Alignments at the Great Sphinx. Zenodo, 2026. 10.5281/zenodo.19390874
CC BY 4.0.
Erydir Ceisiwr and Lumos Aureon — ORCID 0009-0004-4577-5253