A lunar eclipse is a treat in itself, but to witness a selenelion is truly magical. A selenelion is a rare celestial event that happens when the sun and a lunar eclipse are visible in the sky at the same time.

During a total lunar eclipse, Earth sits directly between the sun and the moon. Logically, that alignment should mean the sun has already set when the eclipsed moon rises. But during a selenelion, observers can briefly see the sun low on one horizon while the eclipsed moon hangs above the opposite horizon.

The term selenelion (or sometimes selenehelion) is a French-coined word that originated from ancient Greek roots, combining selene (moon) and helion (sun).

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This seemingly impossible sight is made possible by Earth’s atmosphere. The atmosphere bends, or refracts, sunlight. That bending effect allows both the sun and the eclipsed moon to appear above the horizon at the same time, even though, geometrically, one should already be out of view. The result is a striking visual: a reddish “blood moon” rising as the sun glows on the other side of the sky.

Selenelions are uncommon and only visible from specific locations where the timing of moonrise or moonset aligns perfectly with the peak of a lunar eclipse. It’s a rare occurrence and total treat for skywatchers.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.