A blue micromoon will make a rare appearance this weekend, offering skywatchers a sight they won't have a chance to witness again until the very end of 2028. 

The blue micromoon is a blue moon that's the most distant and smallest-looking full moon of the year.

In the Northern Hemisphere, people will see the upcoming spectacle occur alongside Antares, a bright star that will appear in the constellation Scorpius. The scene could be especially thrilling south of the equator and across the Pacific, as the moon will appear to cross in front of Antares and obscure it, astronomers said. 

Occurring once every two or three years, a blue moon is how scientists refer to the second full moon of a single month. This month, the first full moon happened on May 1. The last blue moon emerged in 2023, and the next one won't arrive until December 31, 2028, according to EarthSky.

Despite the name, this blue moon won't appear turquoise, sapphire or any other shade. The term simply refers to the uncommon occurrence of two full moons in one month.

Since the moon's orbit isn't a perfect circle, the upcoming full moon will be farther from Earth than usual at a distance of 252,360 miles, making it seem a bit smaller and dimmer. It's the opposite of a supermoon when a full moon comes closer to us than normal. The most recent supermoon, by comparison, was just 225,130 miles away.

How to see the blue micromoon

Those who want to see the blue micromoon will have to intentionally go looking for it. The Virtual Telescope Project's Gianluca Masi told the Associated Press that the micromoon will appear 6% smaller and 10% dimmer, roughly, than an average full moon. Because of that, the differences "are subtle enough to likely go unnoticed by most observers."

The Virtual Telescope Project said it will stream live images of the blue micromoon, captured by its robotic telescopes.

People looking up from the Southern Hemisphere may see a bit more action that those in other places. For stargazers in Argentina, Chile, New Zealand, eastern Australia, parts of Antarctica and a smattering of other islands, Antares will vanish temporarily as the blue micromoon passes in front of it.

The red supergiant star, 550 light-years away, is known as the "heart of scorpion" in the constellation Scorpius. A light-year is almost 6 trillion miles.

There won't be any disappearing act for those looking up elsewhere in the world, with Antares constantly visible alongside the full moon.