The second full moon of May 2026 will occur on May 31. This full moon is referred to as a "Blue Moon" because it is the second full moon in a single calendar month, an event that occurs approximately every 2.5 years. This full moon is also a "micromoon," as its orbit brings it near its farthest point from Earth (apogee). The moon will not appear blue in color. In parts of the Southern Hemisphere, the moon will pass in front of the star Antares in an event known as an occultation.
Event Timing and Visibility
The full moon will reach peak illumination at 4:45 a.m. EDT (0845 GMT) on May 31. In the United States, the moon will rise above the eastern horizon around sunset on May 30. The Virtual Telescope Project will host a free livestream of the event. The broadcast begins at 9:30 p.m. EDT on May 30 (0130 GMT on May 31) and will be available on Space.com, the Virtual Telescope Project's WebTV, and its YouTube channel, weather permitting. The stream will include archival images of the moon above landmarks in Rome, Italy.
Technical Details of the Micromoon
This full moon is the smallest of the year because it occurs 19 hours before lunar apogee, the moon's farthest point from Earth in its orbit. At apogee, the moon will be at a distance of approximately 252,360 miles (406,135 km) from Earth. Compared to an average full moon, a micromoon appears about 6% to 7% smaller and up to 10% dimmer, though these differences are subtle and may go unnoticed by most observers. A micromoon is the opposite of a supermoon.
Celestial Alignments
- The red supergiant star Antares, located in the constellation Scorpius, will appear close to the lower left of the moon for observers in the Northern Hemisphere.
- The planets Jupiter, Venus, and Mercury will form a line above the western horizon in the glow of the setting sun.
Antares Occultation
In parts of the Southern Hemisphere, the moon will pass directly in front of Antares, an event known as an occultation, temporarily obscuring the star's light. This occultation will be visible from regions including southwestern Australia, New Zealand, Fiji, Argentina, and Chile. In the Northern Hemisphere, the moon and Antares will appear close together but no occultation will occur.
Definitions
- Blue Moon: A term that can refer to either the third full moon in a season with four full moons (seasonal) or the second full moon in a calendar month (monthly). The May 31 full moon is a monthly Blue Moon.
- Micromoon: A full moon that occurs near apogee, appearing smaller and dimmer than an average full moon.
- Occultation: An event in which the moon passes directly in front of a star, briefly hiding its light.
The next Blue Moon is scheduled for May 2028. The next Blue Micromoon event is scheduled to occur on December 31, 2028, according to EarthSky.