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A rare "blue moon," October's second full moon, will light up the Halloween night sky

Super Blue Blood Moon
Best images of the Super Blue Blood Moon 01:31

Between a once-in-a-lifetime comet and a near-miss with an extremely close asteroid, 2020 has been a strange year for outer space. And October is no exception, bringing a rare blue moon just in time for Halloween.

As some trick-or-treaters stay indoors due to coronavirus safety concerns, October has brought not one but two full moons — a phenomenon known as a "blue moon" — which occurs about once every two and a half years, according to NASA.

Blue moons occur because the lunar cycle and the calendar year are not perfectly synced. Full moons come every 29 days, while most months are 30 or 31 days. The Americas last saw a blue moon in March 2018.

NEWS: MAR 31 Full Blue Moon
A full Blue Moon is seen on March 31, 2018, in Millburn, New Jersey. Rich Graessle/Icon Sportswire via Getty Images

The first full moon of the month occurred on October 1. This year, it was known as the Harvest moon, because it was the full moon closest to the autumn equinox.

The second full moon peaks at 10:49 a.m. ET on October 31, creating a spooky backdrop for an unusual Halloween. According to Farmer's Almanac, the last Halloween full moon occurred in 2001, but only for central and pacific time zones.

This year marks the first time a Halloween full moon has been visible in all time zones since 1944 — meaning every person around the world will experience the Halloween blue moon together for the first time since World War II.

This moon is also known as the Hunter's moon, which is the first moon following the harvest moon. It was likely named for the time of year to go hunting in preparation for winter. Other names include the Blood moon, Sanguine moon, Travel moon and Dying Grass moon.

Unfortunately, it won't actually appear blue — the date of a full moon does not affect the moon's color. But wildfires can affect the moon's color, so it is possible that skywatchers in the western U.S. may see either a blue blue moon or a red blue moon next month.

A Blue Moon won't return until August 31, 2023.

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