Eye On The Night Sky For Friday, March 27

I'm Mark Breen.

Welcome to Night Sky for Friday, March 27.

The Earth's tilted axis vary very slowly pivots so that the North and South ends gradually

circumscribe a circle over a cycle of 26,000 years.

The North star changes, but it does circle back in 26,000 years to Polaris once again.

The Southern skies lack a South Star, but starting in 3,000 years an extended period of various

South stars lasts 8 millennia.

But why this pivot, why this cycle?

The Earth is not a perfect sphere, but an oblate spheroid, a fancy way of saying the Earth

bulges near the equator in its flattened slightly at the poles.

In addition, the Earth's tilted axis means the bulges located a little higher or lower

than our orbital plane.

The Sun exerts a slightly greater gravitational pull on that equatorial bulge, creating

an imbalance of forces.

Since our orbit changes that location, it induces a slight pivot and sets things into

motion.

Next week, the full moon suggests we concentrate on the brighter stars on Night Sky.

Night Sky is a production of Vermont Public and the Fairbanks Museum and Planetarium.