A rare blue moon is set to illuminate the skies this weekend — although it won’t actually be blue.
The celestial phenomenon is expected to peak on May 31, marking the month’s second full moon after the flower moon on May 1. It will also be a micromoon, which means it may appear slightly smaller and dimmer than usual.
Here is everything you need to know about when to see it.
What time will the blue moon peak?
The 2026 blue moon will reach peak illumination at 4:45 a.m. ET on May 31, although it will appear full from the night of May 30.
It should be visible without telescopes or special equipment, weather permitting. Skywatchers will get the best views away from city lights and under clear skies.
Venus and Jupiter will be visible in the western sky about an hour after sunset, according to AccuWeather. Early risers can also catch Mars and Saturn low in the eastern sky in the hour before dawn.
What color is a blue moon?
Despite the name, the blue moon will look much like any other full moon.
The phrase refers to the timing of the lunar cycle, rather than the moon’s color. A blue moon is the second full moon in a single calendar month.
According to Encyclopedia Britannica, the term originated in the 16th-century expression “the moon is blue,” which meant something impossible. The phrase “once in a blue moon” is now used to describe a rare event.
How rare are blue moons?
Calendar blue moons occur roughly every two to three years, according to NASA. The last one appeared in August 2023, and another won’t occur again until 2028.
The phenomenon happens because the lunar cycle lasts about 29.5 days — slightly shorter than most calendar months — which occasionally allows two full moons to occur in a single month.
A diagram showing the phases of the Earth’s moon.
(Ron Miller/Stocktrek Images via Getty Images)
There is also another type of blue moon, sometimes called a seasonal blue moon. This refers to the third full moon in a season containing four full moons. The next seasonal blue moon will be visible in May 2027.
What is a micromoon?
A micromoon occurs when the full moon is near the farthest point in its orbit around Earth.
The Virtual Telescope Project’s Gianluca Masi said Sunday’s micromoon will appear about 6% smaller and 10% dimmer than that of an average full moon. These differences will be “subtle enough to likely go unnoticed by most observers,” he told AP.
The combination of a blue moon and a micromoon is relatively uncommon, making this weekend’s event noteworthy.
What is Antares?
Antares, a red supergiant star in the constellation Scorpius, will appear close to the moon throughout the weekend. It sits 550 light-years from Earth and is one of the largest stars visible to the naked eye.
For most skywatchers, Antares will simply be a bright companion to the full moon.
However, those in Argentina, Chile, New Zealand, eastern Australia and parts of Antarctica will witness a lunar occultation, where the moon passes directly in front of the star, briefly blocking it from view.
