The Earth's rotation axis is not fixed in space; it is moving like the top of a wobbly top
a.i) By human standards, this conical motion is imperceptible--with a precession period of 26,000 years,
it takes 26,000 years for the Earth's axis to do a full rotation.
Another way to look at this is that right now the North Star is Polaris, but in 13,000 years the star
Vega will be approximately at the North Celestial Pole.
Then in 26,000 years, the pole will be pointing in the same direction again--back at Polaris.
The twenty brightest stars as seen from Earth are classified in that manner because they have high
Luminosity and/or are nearby.
a.i) Those stars are: Sun, Sirius, Canopus, Arcturus, Alpha Centauri, Vega, Rigel, Procyon, Achernar,
Betelgeuse, Hadar (Agena), Capella A, Altair, Aldebaran, Capella B, Spica, Antares, Pollux,
Fomalhaut, and Deneb.