Tonight's harvest supermoon will be about 22,600 kilometres closer to Earth than usual, making it appear about 5 per cent larger and 13 per cent brighter than the average full moon.
Here's how to see it in Australia.
When is the September harvest supermoon and how can I see it?
The moon will reach its fullest point at 7:57pm (AEST) on Friday, September 29, according to the Sydney Observatory.
However, don't fret if you miss out on viewing it at that exact moment – NASA says the moon will also appear full on Saturday night.
Generally speaking, full moons are best to view when they're passing horizon, as it's then when they appear to be largest.
Moonrise will happen at different times depending on where you are in the country – 5:45pm in Sydney, 6:11pm in Melbourne, 5:37pm in Brisbane, 6:08pm in Adelaide and 6:13pm in Perth (all local times).
What actually is a supermoon?
Definitions of a supermoon can vary, but the term generally applies to a full moon that is closer to Earth than normal and thus appears larger and brighter in the night sky.
Tonight's moon will be 361,867 kilometers away from Earth, about 22,604 kilometers closer than its average distance.
The closest supermoon of the year occurred on August 30, when the moon was just 357,200 kilometers away from Earth.
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September's full moon will appear about 5 per cent bigger and 13 per cent brighter than the average full moon, according to NASA.
Some astronomers say the phenomenon occurs when the moon is within 90 per cent of perigee – its closest approach to Earth in orbit.
Why is this one called the harvest supermoon?
The name harvest moon is a nod to the season of gathering because the event occurs close to the beginning of the northern hemisphere's fall, or the autumnal equinox, which fell on September 23.
Typically, this time of year is when many crops peak in the Northern Hemisphere, and the bright moon once helped farmers work into the evening to harvest their bounty ahead of the first frost, according to The Old Farmer's Almanac.
Other monikers for September's full moon across the USA's different Indigenous tribes include the corn maker moon from the Abenaki tribe, the moon of the brown leaves from the Lakota people and autumn moon from the Passamaquoddy tribe.
Many people associate the harvest moon with being orange in colour as it begins to rise, but the same could be said of all full moons.
The hue is due to the thickness of Earth's atmosphere near the horizon, which is greater than when the full moon is overhead, according to EarthSky.
– With CNN
