A Smaller Than Usual Blue Moon Will End the Month With a Lunar Spectacle. Here’s What to Know About the Full Micromoon

The blue moon will be the second of two full moons in the same month, a coincidence that only takes place about every two and a half years. It will also appear to be slightly smaller and dimmer than the average full moon

Margherita Bassi | Daily Correspondent

May 28, 2026 3:40 p.m.

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

This year, May is bookended by two full moons. So, on Sunday, the month’s closing spectacle will be a once-in-a-blue-moon event—literally. The second full moon, known as a blue moon, will grace Earth’s sky on May 31, representing a relatively rare astronomical phenomenon and highlighting a historical incident that gave the event its name.

The moon completes a cycle, or goes through all its phases, once every 29.5 days. As such, even though most calendar months feature only a single full moon, there can sometimes be two if the first one takes place at the very beginning of the month. The second of these is known as a blue moon—though it isn’t actually blue in color. This is technically called a calendrical or monthly blue moon.

A seasonal blue moon, on the other hand, is the third of four full moons in an astronomical season, which is dictated by solstices and equinoxes and usually has only three full moons, per the Old Farmer’s Almanac.

According to the publication, people pay more attention to the calendrical blue moon than to its seasonal counterpart, even though the phrase “blue moon” initially referred to the seasonal occurrence before it ever gained a second definition.

“The modern understanding of ‘blue moon’ only took off in the 1980s,” reports the almanac. “It was a result of a much earlier mistake printed in a 1946 issue of Sky & Telescope magazine, and since then, the term has gone viral in the media.” Although people will say “once in a blue moon” to describe a rare event, calendrical blue moons are not all that unusual. They take place every two and a half years, on average.

This Sunday’s moon, however, is special in more ways than one. It will be the smallest full moon of 2026. Of course, the moon itself isn’t actually a different size—it only appears to be, because it’s farther away. The moon doesn’t orbit in a perfect circle, so its distance from our planet varies throughout the lunar cycle. This more distant blue moon is considered a micromoon—an unofficial term for a full moon or new moon that occurs at or near the moon’s farthest point from Earth in its orbit, called the apogee.

Compared to an average full moon, Earth’s satellite will seem around 6 percent smaller and 10 percent dimmer during this micromoon, as Gianluca Masi, an astronomer and founder of the Virtual Telescope Project, tells the Associated Press’ Marcia Dunn. These are “differences that are subtle enough to likely go unnoticed by most observers,” he adds.

So, while the micromoon is an interesting phenomenon to note, it might not be apparent to the eye. But “careful observers or photographers can detect it,” says Seth McGowan, president of the Adirondack Sky Center in New York, to National Geographic’s Stefanie Waldek.

The last monthly blue moon was on August 19, 2024, and in that case it was a super blue moon, according to USA Today’s Julia Gomez. A supermoon is the opposite of a micromoon—it’s when a full moon takes place at or near perigee, the lunar orbit’s closest point to Earth.

The moon’s next apogee will be on June 1, and the last one was on May 4, meaning the full moon that began the month was also a micromoon.

Margherita Bassi | Read More

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.