Moving South

Alpha Sextantis is moving south. The star crossed the celestial equator less than a century ago. It’ll continue moving southward for millennia.

The star is fairly impressive. It’s about three times as massive as the Sun, and more than a hundred times brighter. That makes it visible to the naked eye even though it’s about 280 light-years away.

Perhaps the most notable thing about Alpha Sextantis, though, is its location: It’s only a quarter of a degree south of the celestial equator — the projection of Earth’s equator on the sky.

In 1923, the star crossed the equator from north to south. The star wasn’t responsible for the shift, though. Instead, the equator is moving.

That’s because the pull of the Sun and Moon cause Earth to wobble like a spinning gyroscope. It takes about 26,000 years to make one full wobble. During that time, we have different pole stars.

The stars also drift across the seasons. And the equator moves north and south across the sky, so the stars move north and south as well.

Alpha Sextantis will continue moving southward for thousands of years. Then it’ll reverse course. It’ll cross the equator around the year 18,000 — returning once again to the northern half of the sky.

Alpha Sextantis is in the constellation Sextans, the sextant. It’s in the southeast as night falls. Under dark skies, Alpha Sextantis is just visible. It’s to the lower right of Regulus, the bright heart of the lion.

Script by Damond Benningfield