On Sunday night, the air will be cold and the sky will be clear for most of the country as a total lunar eclipse bathes the moon in an eerie blood-red hue. From Hawaii to Maine, all 50 states will have a chance to see it — the most widely visible lunar eclipse in the United States since October 2014.
Oh, and it will be a supermoon, meaning it will be ever so slightly closer to Earth than normal.
Lunar eclipses occur when Earth passes directly between the sun and the moon, forming a perfect line. This year, the moon will be high in the sky, which makes it the best chance to watch an eclipse in years.
The total eclipse will begin in the Central time zone at 10:41 p.m. and reach totality at 11:13 p.m., ending at 11:43 p.m.
During totality, no sunlight reaches the moon, because the Earth blocks all the rays. The only reason the moon is visible is because some of the light is refracted, or bent, around the edges of the globe and toward the moon. The reddening of the moon is akin to what makes sunsets so spectacular, with pink and orange hues. Green and blue don’t make it through, scattered away by the particles in the Earth’s atmosphere. The only light wavelength left is red — dimly illuminating the moon with less than one-thousandth of the full moon’s normal brightness.
It’s difficult to predict the exact hue of lunar eclipses, but whatever shade results can offer insight about the chemistry of the Earth’s atmosphere. A maroon or auburn tinge have been known to result when the atmosphere is particularly polluted, often in the wake of large volcanic eruptions. Particles in the atmosphere generate more clouds, boosting the number of small water droplets in the air, and the tiny drops of water in clouds scatter light very well.
On top of changing colors, the moon will be super. (Not that it isn’t super already — we love our only natural satellite.) This recently popular but decades-old term is used to describe a full or new moon that is closest to Earth in its orbit, which is the shape of an ellipse, just like Earth’s orbit is an ellipse around the sun. You probably won’t be able to notice the difference in the size or the brightness of the moon, but it is noteworthy enough as an astronomical event. The next extreme supermoon, when the moon is as close to the Earth as it can be, will be Jan. 21, 2023.