Look up into the sky tonight and you'll witness the first, and last, supermoon of 2017. Supermoons occur when the moon is full at the same time it reaches its perigee, the point in its orbit when it's closest to Earth, Space.com reports. At about 3:45am EST tomorrow morning, the moon will be a mere 238,000 miles from us, about 16,000 miles closer than its average distance. And since it will have become totally full less than 24 hours earlier, the moon will appear up to 14 percent larger and 30 percent brighter in the sky.
If you want to add to the effect, Robert Massey of the Royal Astronomical Society told the BBC that the best to time to see the supermoon will be when it's setting tomorrow. What astronomers call the "moon illusion" will make the moon appear even larger as it gets closer to the horizon. NASA is calling tonight's supermoon the first in a trilogy. There will also be supermoons on Jan. 1 and 31. And since the Jan. 31 full moon will be the second in the same month, it will be an extremely rare Super Blue Moon. (Read more supermoon stories.)