Supermoon and lunar eclipse will light up and darken Tuesday's night sky

Tonight stargazers across North America will be gifted with two astronomical events as both a supermoon and a partial lunar eclipse will be visible .

Those observing will be in for a rare treat. September's full moon happens to be a supermoon as well as this year's Harvest Moon, coinciding with a partial lunar eclipse.

But what exactly is a supermoon and a lunar eclipse and when is the best time to catch them?

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What is a supermoon?

A supermoon is a full moon that occurs when the moon is at the closest point in its orbit around Earth known as perigree. When the moon is at perigree it can appear up to 14 percent larger and 30 percent brighter that it normally does.

The term "supermoon" was coined by astrologer Richard Nolle in 1979 as either a new or full Moon that occurs when the Moon is within 90% of its closest to Earth, according to NASA. This supermoon will be nearly about 222,000 miles from Earth.

While full moons occur once in each lunar cycle which last 29.5 days, there are usually only about three or four supermoons annually. There are two more supermoons left in 2024, with the next one expected on Oct. 17 and Nov. 15.

This supermoon also happens to be a Harvest Moon. It is the full moon closest to the fall equinox- which happens to land on Sept. 22 this year.

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What is a partial lunar eclipse?

A partial lunar eclipse occurs when the moon passes through only one part of the Earth's dark, inner shadow called the umbra. The shadow grows and then recedes without ever entirely covering the Moon.

“You’ll see the shadow of the Earth start to eat into the moon, “ Bruce Betts, the chief scientist at the Planetary Society, told the New York Times . "like taking a small, dark bite out of the moon.”

This is in comparison to a total lunar eclipse where the Earth’s full shadow falls across the face of the Moon. This partial lunar eclipse is expected to be visible by people in North America, South America, Africa and Europe.

When will it be visible?

Tonight's super moon will reach peak illumination in the U.S. on Tuesday, Sept. 17, at 10:35 p.m. ET, according to NASA . This will coincide with a partial lunar eclipse. The moon is set to enter the Earth's partial shadow at 8:41 p.m. E.T., and the full shadow at 10:13 p.m.

The moon will finish exiting the full shadow at 11:16 p.m. and the partial shadow on Wednesday morning at 12:47 p.m., according to NASA.