On Sunday, stargazers, astronomers and curious sky-watchers will get a chance to witness the first and only supermoon of 2017.
In November 2016, the moon reached a distance closest to the Earth than ever seen since 1948, producing a supersized supermoon. However, on Sunday night, the moon will still shine 16% brighter and appear 7% larger than its usual size.
This supermoon will be the first in the series of three consecutive full moon supermoons, the next two to occur in January.
While it has been a year since a visible supermoon last lit up the sky, everyone in the world has a chance to marvel at this upcoming full moon. Most astronomers suggest watching the supermoon right after sunset and into moonrise.
Also, if you are up before sunrise you will also get the chance to see the phenomenon.
But for those who can’t wake up that early, the moon will still look bigger — and brighter — throughout the night.
Supermoons are a rare type of full moon. They appear up to 14% bigger and 30% brighter than normal. While the full moon rises about once per month, supermoons can only occur a few times per year.
That’s because the timing has to be just right. The Moon takes about 27.32 days to orbit Earth. During its orbit, the moon passes through two points: Perigee and apogee. Perigee is about 30,000 miles closer to Earth than apogee.
A supermoon can only occur at perigee-syzygy, when the moon is full and at perigee simultaneously. This is rare because as the Earth revolves around the sun. the moon’s orientation to Earth stays mostly the same. This changes where the Moon is in orbit during each full moon. But supermoons would even more rare if the moon didn’t precess. Over many years, the moon’s precession changes its orientation slightly.
It’s often hard to differentiate a supermoon and a regular full moon. The best time to watch a supermoon is when it’s low, near the horizon.