The Moon will step on the head of the scorpion tonight. It will pass directly in front of one of the stars that outlines the head, blocking it from view – an event called an occultation.

Pi Scorpii is actually a system of three stars, about 600 light-years away. The main star in the system is about a dozen times the mass of the Sun, and more than 20,000 times the Sun’s brightness. Because of its great mass, it’s already nearing the end of its life, even though it’s billions of years younger than the Sun. Before long, it will explode as a supernova.

The Moon sometimes passes in front of the star because Pi Scorpii lies near the ecliptic – the Sun’s path across the sky. The Moon’s orbit around Earth is tilted a bit, so it roams a few degrees either side of the ecliptic. That allows it to occult quite a few stars that are bright enough to see with the unaided eye.

This month alone, in fact, the Moon will stage almost a dozen occultations. But each of them is visible across only a small slice of the globe, so we don’t see all of them from here in the United States. But some of them align just right – allowing us to see the Moon briefly stomp out a star.

The occultation of Pi Scorpii will be visible across almost all of the Lower 48 states. The exact time, and how long the star remains blocked, depends on your location.

We’ll talk about the Moon and the heart of the scorpion tomorrow.

Script by Damond Benningfield