Halloween's Rare Blue Moon Will Coincide with Uranus at Opposition and a 200-Foot Asteroid Flyby

This Halloween, a rare blue moon will coincide with Uranus reaching opposition as well as a 200-foot-wide asteroid making a close approach to Earth.

Every so often, a single calendar month will feature two full moons—the second of which is always referred to as a "blue moon."

This is the case in October 2020 given that a full moon appeared on October 1, and another is set to grace the skies on Halloween.

A full moon on Halloween occurs approximately every 19 years due to a lunar pattern known as the Metonic Cycle, according to the Farmer's Almanac. After this period of time, the phases of the moon recur on the same day of the year.

Thanks to this cycle, the last full moon on Halloween appeared in 2001 and the next won't be seen until 2039.

But a Halloween full moon hasn't actually appeared across all U.S. time zones since 1944, according to the Almanac. Blue moons occur on average every two-and-half to three years.

The full moon on Halloween will appear "opposite" the sun with the Earth located directly in between at 10:49 a.m ET, at which point it will be fully illuminated—although it will look full to most observers from Thursday night through Sunday night—according to NASA.

October 31 will also see Uranus reach opposition. This means Earth will be directly in between the sun and the gas giant.

At this time, the blue-green planet will be at its closest point to Earth and its face will be fully illuminated by the sun, shining brighter than at any other time of year. This is the best time to view the planet, which will be illuminated all night long.

Uranus may be barely visible as a tiny dot with the naked eye, but for best viewing you will need a pair of binoculars or a telescope. The planet will be located close to the constellation Cetus.

These astronomical events will take place as a large asteroid flies past the Earth at 2:24 a.m. UTC on October 31 or 10:24 p.m. ET on October 30, according to NASA's Center for Near Earth Object Studies.

At this time, the space rock—called 2020 UX3—will come within around 3.2 million miles of our planet, so it poses no risk to us. This is equivalent to around 13 times the average distance between Earth and the moon.

The asteroid is estimated to measure up to 196 feet in diameter and is travelling at around 36,000 miles per hour.

full moon
A full moon rises behind the Empire State Building in New York City on October 1, 2020, as seen from Union City, New Jersey. For the first time since 2001, a full moon will coincide with Halloween. Gary Hershorn/Getty Images