Equinox and the Full Moon: this week on the Storyteller's Night Sky

Mar 18, 2019

A waning Winter sunset over Lake Michigan, while the Moon waxes Full. Catch Sun and Moon on opposite horizons for 20 minutes Wednesday evening, March 20th, the first day of Spring.

A magic moment is upon us this week when the Sun appears to cross the Celestial Equator heading north, bearing greater daylight in its wake. There's also a curious thing happening with the Moon the very same day.

According to the Astronomy Department of the US Naval Observatory, the Equinox moment will happen at 5:58 pm on Thursday, March 20th. But wait, isn't Equinox always on March 21st?

The answer will take some explaining, so here we go. The Earth exhibits three motions: it rotates on its axis, giving us the experience of day and night; it's orbiting the Sun, defining our yearly cycle with its seasons; and it wobbles. This slow wobble is what causes the moment of Equinox to change over time, in a motion that is referred to as "precession."

And here's what's really interesting about it this year: Just a few hours after the Sun crosses the Celestial Equator, the Moon will come to its Full Phase, the first one of the Spring, at 9:44 pm, also on March 20th. Technically this Moon should appear below the Celestial Equator, since Full Moon is always opposite the Sun, but on March 20th, it's not quite there, and because it's still above the Celestial Equator, it hasn't quite acquiesced its Winter position.

On Wednesday night you'll see the Moon just below the star Denebola, at the tail-end of the constellation Leo, the Lion. Denebola has the reputation of being out of step, of not conforming with the mainstream and of seeing the world through different eyes, or with a different philosophy. 

So if you decide to use the March 20th Moon to mark your Spring festivals of renewal, even though it hasn't fully left its Winter position, know that you are in keeping with the mood of this star.