NEW YORK (AP) — The last supermoon of the year will shine soon in December skies.

The moon’s orbit around the Earth isn’t a perfect circle so it gets nearer and farther as it swings around. When a full moon is closer to Earth in its orbit, a so-called supermoon happens. It makes the moon look up to 14% bigger and 30% brighter than the faintest moon of the year, according to NASA.

Supermoons happen a few times a year in clusters, taking advantage of the sweet spot in the moon’s elliptical orbit, and Thursday night’s event is the last of three in a row in 2025.

The supermoon can be glimpsed in clear night skies without any special equipment. But it can be tough to discern the subtle change with the naked eye.

Whether a supermoon or not, the moon also appears bigger when it’s close to the horizon because of what’s called the moon illusion. It’s a strange visual trick that experts can’t yet explain.

“When you have a supermoon, that effect is just slightly more striking,” said astronomer William Alston with the University of Hertfordshire.

Tides could be slightly higher during a supermoon because the moon is closer to Earth, but again, the difference isn’t very noticeable.

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