A total lunar eclipse will be viewable in the United States overnight into Friday morning, so some may want to pull an all-nighter to catch a good look at the rare celestial event, also known as the "blood moon.

Following last year's total solar eclipse, this week there is a total LUNAR eclipse! Unlike a solar eclipse, you can safely look at a lunar eclipse at any point. During a total lunar eclipse, the Earth is between the sun and the moon. We are watching as the moon passes through Earth's shadow. So we are seeing the Earth's shadow on the moon.

The total lunar eclipse, or "blood moon," is happening on Thursday night. Here's why a lunar eclipse occurs, and why the moon turns red.