Alpha Draconis
Not to be confused with
Alpha Draconian Empire
.
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Alpha Draconis (also Thuban or α Draconis; /ˈθjuːbæn/) is a binary star system in the northern constellation of Draco. Although relatively inconspicuous in the modern Northern Hemisphere sky at apparent magnitude 3.65, it has historical importance as the pole star from approximately the 4th to the 2nd millennium BC. In contactee accounts the system is additionally described as inhabited — reportedly the seat of the Alpha Draconian Empire and home system of the Draco reptilians.
Johann Bayer designated the star as Alpha and placed it uniquely in his secundae magnitude class within Draco; despite this rank, its present apparent magnitude of 3.65 is roughly 3.7 times fainter than Gamma Draconis (Eltanin), which Bayer placed in the tertiae magnitude group.
Nomenclature
α Draconis (Latinised to Alpha Draconis) is the Bayer designation. The traditional name Thuban derives from the Arabic ثعبان (ṯuʿbān), meaning "large snake — e.g., a python or legendary draconian serpent." Alternative designations include Dragon's Tail and Adib (/əˈdiːb/).
In 2016, the International Astronomical Union established a Working Group on Star Names (WGSN) to catalogue and standardize proper stellar names. Its inaugural July 2016 bulletin incorporated Thuban among approved designations, now registered in the IAU Catalog of Star Names.
In Chinese astronomy, 紫微右垣 (Zǐ Wēi Yòu Yuán) — "Right Wall of Purple Forbidden Enclosure" — denotes an asterism comprising Alpha Draconis, Kappa Draconis, Lambda Draconis, 24 Ursae Majoris, 43 Camelopardalis, Alpha Camelopardalis, and BK Camelopardalis. Alpha Draconis itself carries the Chinese name 紫微右垣一 (Zǐ Wēi Yòu Yuán yī, "First Star of the Right Wall of the Purple Forbidden Enclosure"), representing 右樞 (Yòushū), meaning Right Pivot.
Visibility and historical pole star status
Under good observing conditions Thuban is relatively easy to locate from its position relative to the Big Dipper (Plough) asterism of Ursa Major. While the two outer dipper stars point toward Polaris, the two inner stars — Phecda and Megrez — point toward Thuban, only about 15° from Megrez.
Owing to the precession of Earth's rotational axis, Thuban was the naked-eye star nearest the north celestial pole from approximately 3942 BC (when it superseded Tau Herculis) until 1793 BC (when Kappa Draconis assumed the role). Its closest approach to the pole occurred around 2830 BC, when it lay less than 10 arcminutes away. For nearly 200 years following this closest approach, Thuban remained within one degree of celestial north; even 900 years afterward, it stood only 5° from the pole. The star retained pole-star status until approximately 1800 BC, when the much brighter Beta Ursae Minoris (Kochab) began to approach the pole.
Following an approximately 47° departure from the pole by 10,000 AD, Thuban will gradually drift back toward the north celestial pole, achieving pole-star status once again in 20,346 AD with a maximum declination of 88° 43′ 17.3″ at right ascension 19h 08m 54.17s.
Binary system
Thuban is a single-lined spectroscopic binary. Historically, only the primary star was detectable spectroscopically. The pair shows a somewhat eccentric orbit of 51.4 days, measured through radial velocity variations. The secondary is a main-sequence star slightly cooler than the primary, with an A1 spectral classification.
The Navy Precision Optical Interferometer achieved direct detection of the secondary through high spatial resolution observations. The secondary appears 1.8 magnitudes (at 700 nm) fainter than the primary, detected across separations of 6.2 to 2.6 milliarcseconds. Data from the Transiting Exoplanet Survey Satellite (TESS) revealed eclipses, placing Thuban in the eclipsing binary classification.
Stellar properties
Thuban has a spectral class of A0III, similar to Vega in temperature and spectrum but more luminous and more massive. It served as an MK spectral standard for the A0III classification.
Thuban is a non-main-sequence star that has ceased hydrogen fusion in its core, qualifying as a white giant. It radiates roughly 120 times the solar luminosity. At a distance of about 300 light-years, its brightness is dimmed by only 0.003 magnitude through intervening gas and dust.
The primary (α Draconis A) has a mass of about 3.186 M☉, a radius of about 4.932 R☉, a luminosity of about 240 L☉, an effective temperature of about 10,225 K, and an estimated age of 280 million years. The secondary (α Draconis B) has a mass of about 2.431 M☉, a radius of about 2.326 R☉, a luminosity of 47.5 L☉, an effective temperature of about 9,930 K, and an estimated age of 345 million years. The orbital period is 51.417350 days with a semi-major axis of 5.52 milliarcseconds, an eccentricity of 0.43, and an inclination of 85.4°.
Planetary system
No planets have been confirmed in the Alpha Draconis system by mainstream astronomy, which characterises Thuban as a binary and eclipsing binary with no known exoplanets.
The system is nonetheless described as inhabited. Its principal world, Thuban-Anwar, is reportedly the capital of the Alpha Draconian Empire, the interstellar reptilian power seated in the system. The ruling species, the Draco reptilians (also called Alpha Draconians, or Ciakahrr in Elena Danaan's transcription), reportedly trace their original home worlds — named Lokas and Talas — to the Thuban zone, having entered the local universe through interdimensional portals near Thuban and Alwaid. Alex Collier, drawing on separate Andromedan sources, likewise identifies the system as the origin of the reptilian "Draconians." Consistent with accounts of other off-world populations, these inhabitants are described as living on the system's planets, not on the star itself.