After an absence of about two and a half years, the Moon is preparing to transform into a Blood Moon. Observers looking up at the sky this Thursday night will witness the Earth’s satellite taking on a reddish color.

The term Blood Moon is non-scientific and describes the reddish color resembling rust that the moon takes on during a lunar eclipse. More rarely, this term is also used to refer to four total lunar eclipses that can be observed from a specific point within two years.

According to Sciencealert, this event presents a great opportunity for sky watchers, as witnessing four consecutive eclipses is a rare occurrence despite usually being able to observe four to five total lunar eclipses from the same spot over ten years.

WHY DOES THE BLOOD MOON APPEAR RED? The Earth blocks sunlight by casting a shadow into space. However, the atmosphere allows a certain amount of light to pass through. While gases in the atmosphere scatter some light, particles in the air reflect specific wavelengths more. Particularly, longer red wavelengths tend to be scattered instead of shorter blue wavelengths. Hence, just like during sunrise and sunset, a reddish hue forms during a lunar eclipse. A rust-colored glow appears at the edges of the shadow cone created by Earth, and the Moon becomes tinged with red.

WHEN CAN THE BLOOD MOON BE OBSERVED? The Moon passes through the Earth’s shadow only a few times a year due to its small size and proximity to Earth. Additionally, the Moon’s orbit has a slight inclination compared to Earth. When direct sunlight is completely blocked, the reddish light passing through Earth’s atmosphere reaches the Moon’s surface, giving it a eerie reddish tint. Occasionally, a rare event known as the “Super Blue Blood Moon” can also occur. This happens when a Super Moon and Blood Moon coincide. To not miss this unique sky event, don’t forget to prepare your telescopes and cameras on Thursday night!