Night sky rarity comes as a Halloween treat

Those looking forward to a spooky Halloween are in for a treat this year: a rare blue moon will rise on Saturday night.

For the first time since World War II, a full moon on Halloween will appear in the night sky on Oct. 31, beginning at 10:49 p.m.

Despite its name, there will be no changes to the actual color of the moon, according to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).

There may be a tinge of blue, however, under certain atmospheric conditions, such as during volcanic eruptions or after exceptionally large fires that leave particles in the atmosphere.

2nd moon in a month

“Whenever two full moons appear in a single month (which happens on average every 2 1/2 to 3 years), the second full moon is called a ‘blue moon,’” Pagasa said in its astronomical diary.

This month’s first full moon occurred on Oct. 2.

“Since the lunar cycle is 29 days and most months have 30 to 31 days, we eventually find a situation where a full moon occurs at the beginning and the ending of the same month,” Pagasa said.

Whether the full moon will be seen across the country will depend on the weather, particularly with a cyclone expected to bring stormy conditions across Luzon during the weekend.

Lunar trifecta

But if the weather turns out to be favorable in your area, it’s best to turn your gaze toward the night sky, since the next Halloween full moon won’t occur in another 19 years.

According to the Farmer’s Almanac, the next full moon rising on Oct. 31 will be in the years 2039, 2058 and 2077, under a pattern known as “Metonic Cycle.”

On Jan. 31, 2018, a rare super blue blood moon was seen when three lunar events occurred simultaneously: the blue moon, supermoon and lunar eclipse.

Reddish hue

A supermoon happens when the moon comes within at least 361,000 kilometers of the Earth while the term blood moon refers to the reddish hue the full moon emits when seen from afar during an eclipse.

The popular definition of blue moon came about after a writer for Sky & Telescope magazine in 1946 misinterpreted the Maine Farmer’s Almanac and labeled a blue moon as the second full moon in a month. In fact, the almanac defined a blue moon as the third full moon in a season with four full moons, not the usual three.

Though Sky & Telescope corrected the error decades later, the definition caught on. —With a report from ANA ROA, Inquirer Research