Planet Earth spins a full 360°, about its axis, every 24 hours.
From either hemisphere, the night sky always rotates about our celestial poles.
The southern hemisphere has no bright “pole star,” but the northern hemisphere has Polaris.
Terminating the Little Dipper’s handle, Polaris lies within 1° of Earth’s true north pole.
But this won’t always be true.
Gravitational tugs lead to precession, causing our tilt’s direction to migrate.
Additionally, our axis “wobbles” over time, varying in inclination.
Over ~26,000 year timescales, our axis completes a 360° rotation.
Bright Polaris will pass within 0.45° of “true north” after 80 more years.
~12,000 years later, Vega becomes Earth’s brightest pole star: within 5° of true north.
5000 years ago, Thuban was the closest pole star of all: within 0.2° of celestial “north.”
Meanwhile, the southern pole has been “starless” for millennia.
Beginning in the year ~5000, a series of excellent “south pole” stars will appear.
The best ones include:
two prominent “False Cross” stars.
In the year ~7000, both poles will simultaneously possess pole stars.
Enjoy Polaris while we have it; after 2102, today’s “North Star” will consistently worsen.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.