Rare Blue Supermoon

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    A supermoon rises through clouds over the skyline of lower Manhattan in New York on August 1, 2023. (AP/Seth Wenig)
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    A plane passes in front of a supermoon on July 13, 2022. (AP/Morry Gash)
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Stargazers are in for a treat this week: a rare blue supermoon plus the planet Saturn peeking out from behind. But the night-sky double feature also has weather forecasters worried. The event coincides with Hurricane Idalia—with the potential to make storm flooding worse.

Wednesday night will showcase the second full Moon of the month. The first full Moon was August 1.

A second full Moon is rare and the reason it’s called “blue.” (Ever heard the idiom “once in a blue Moon” to mean something unusual?) Blue Moons occur only about once every 33 months.

This particular blue Moon is even rarer: It is a “supermoon.” Supermoons are closer to Earth than usual. The nearness makes the satellite appear especially big and bright.

Blue supermoons occur only once every 10-20 years.

As a bonus, Saturn will be also be visible in the night sky on Wednesday. It will appear as a bright point near the upper right of the Moon at sunset in the east-southeastern sky, according to NASA. The ringed planet will appear to circle clockwise around the Moon as the night wears on.

Not only is a blue supermoon rare, but it could also raise tides above normal because of increased gravitational pull. The higher tides come just as Hurricane Idalia lashes Florida’s west coast.

“I would say the timing is pretty bad for this one,” says Brian Haines. He’s the meteorologist in charge at the National Weather Service office in Charleston, South Carolina.

The supermoon is expected to make tidal flooding worse not only in Florida, but also in Georgia and South Carolina.

There won’t be another blue supermoon until 2037, according to Italian astronomer Gianluca Masi. He is founder of the Virtual Telescope Project.

Clouds spoiled Masi’s attempt to livestream the supermoon earlier this month. He hoped for clearer skies this time so he can capture the blue supermoon shining above St. Peter’s Basilica at the Vatican.

“I’m always excited to admire the beauty of the night sky,” says Masi, especially when it features a blue supermoon. Weather permitting, observers don’t need binoculars or telescopes—“just their own eyes.”

If you miss Wednesday night’s view, try again Thursday night. To the naked eye, the Moon will still look just as full.

When I look at your heavens, the work of your fingers, the Moon and the stars, which you have set in place, what is man that you are mindful of him, and the son of man that you care for him? — Psalm 8:3-4