Blue Moon May 31, 2026: Smallest Full Moon & Antares Occult.

Last updated: May 21, 2026. On Sunday, May 31, 2026, at 08:45 UTC, skywatchers will be treated to the second full moon of May. This calendrical blue moon will reach peak illumination at a staggering distance of 406,135 km (252,361 miles) from Earth, officially making it the smallest full moon of 2026. But what truly sets this lunar event apart is the rare Antares lunar occultation 2026 that accompanies it. As the blue moon May 31 2026 crosses the night sky, it will pass directly in front of the bright red supergiant star Antares, offering a spectacular celestial show for observers in the Southern Hemisphere.

At a Glance: Blue Moon May 31 2026

Here are the essential details for the smallest full moon of 2026:

• Date & Peak Time UTC – May 31, 2026, at 08:45 UTC
• Distance from Earth – 406,135 km (252,361 miles) at apogee
• Size Difference – Approximately 6% to 7% smaller than average, and 12% to 14% smaller than a supermoon
• Visibility Regions – Worldwide for the full moon; Southern Hemisphere for the occultation
• Special Feature – The rare Antares lunar occultation 2026

Why It’s Called a Blue Moon (and the 1946 Mistake)

The term "Blue Moon" has a fascinating origin that bridges astronomical folklore and a historical misunderstanding. Today, a monthly Blue Moon refers to the second full moon in a single calendar month. But where did this once in a blue moon meaning come from? It traces back to a March 1946 article in Sky & Telescope titled "Once in a Blue Moon." In it, amateur astronomer James Hugh Pruett of Eugene, Oregon, misinterpreted the Maine Farmers' Almanac's seasonal definition. According to NASA's solar system updates, Pruett's error became standard terminology.

Pruett wrote: "Seven times in 19 years there were — and still are — 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon." As noted by folklorist Philip Hiscock in his March 1999 Sky & Telescope analysis, this definition stuck in popular culture. It is crucial to clarify that the name has absolutely nothing to do with the Moon turning blue in colour. For context, the previous monthly blue moon was the August 19, 2024 Super Blue Moon, marking a 21-month, 12-day gap between these events.

Blue Moon Time IST / EDT / PDT / BST & Local Conversions

To catch the exact moment of peak illumination for the blue moon May 31 2026, you will need to convert the 08:45 UTC peak to your local time zone. Remember that the Moon will appear full to the naked eye for about three days surrounding this exact moment, as confirmed by the Old Farmer's Almanac and timeanddate.com.

Peak times across major global time zones include:

• PDT (Pacific Daylight Time) – 1:45 a.m.
• EDT (Eastern Daylight Time) – 4:45 a.m.
• BRT (Brasília Time) – 5:45 a.m.
• UTC (Coordinated Universal Time) – 08:45 a.m.
• BST (British Summer Time) – 9:45 a.m.
• CEST (Central European Summer Time) – 10:45 a.m.
• IST (Indian Standard Time) – 2:15 p.m. (Moon is below the horizon; best viewing is moonrise on May 30 and May 31)
• JST (Japan Standard Time) – 5:45 p.m.
• AEST (Australian Eastern Standard Time) – 6:45 p.m.
• NZST (New Zealand Standard Time) – 8:45 p.m.

The Smallest Full Moon of 2026: A True Micromoon

While supermoons often dominate space news, the blue moon May 31 2026 is special because it is a blue moon micromoon. This apogee full moon occurs when the Moon is at its farthest point from Earth in its elliptical orbit. At a distance of 406,135 km, it contrasts sharply with the 384,400 km average Earth-Moon distance.

According to Catherine Pilachowski, Distinguished Professor and Daniel Kirkwood Chair in Astronomy at Indiana University Bloomington and former American Astronomical Society President (2002–2004), speaking via TODAY.com, a micromoon is "about 6% to 7% smaller than the average full moon and 12% to 14% smaller than a super moon." However, due to the famous Moon illusion, which makes the Moon look larger near the horizon, the size difference will likely be invisible to the naked eye for casual observers.

The Antares Lunar Occultation 2026

What makes the blue moon May 31 2026 truly spectacular is the Antares lunar occultation 2026. The Moon will pass directly in front of the magnitude 1.0 red supergiant star Antares in the Scorpius constellation. Note a source discrepancy: while the astronomy app Star Walk lists Bolivia in the visibility zone, In-The-Sky.org does not. We credit In-The-Sky.org's JPL DE430-based predictions by Dominic Ford as the authoritative source for this data.

Occultation timings (UTC) by region based on In-The-Sky.org data: Solomon Islands 06:59–07:49; Vanuatu 07:00–08:01; New Caledonia 07:02–08:05; Fiji 07:07–07:58; eastern Australia 07:10–08:13; Norfolk Island 07:13–08:16; Tonga 07:17–08:01; New Zealand 07:17–08:54; Lord Howe Island 07:19–08:15; Tasmania 07:49–08:11; Antarctica 09:46–10:00; Chile 09:56–11:20; Argentina 09:59–11:20; Falkland Islands 10:05–10:45.

"The May 31 Blue Moon is a brilliant teaching moment," says Dr. Ingrid Larsen, Lead Observational Researcher at Zendar Universe. "It perfectly illustrates the ellipticity of the lunar orbit and allows us to separate astronomy from folklore. Watching a micro full moon occult a brilliant star like Antares is a stark reminder of the dynamic, clockwork nature of our solar system."

How and where to watch: Look to the east-southeast after sunset on May 30, or southwest before sunrise on May 31. For astrophotography, use ISO 200–400, a 1/250–1/500 s shutter speed, an aperture of f/5.6–f/8, and set manual focus to infinity. A good pair of binoculars will help you see Antares pop in and out of the Moon's intense glare during the occultation.

Blue Moon vs Flower Moon & Astrological Context

It is important to differentiate the second full moon in May 2026 from the first. The May 1 Flower Moon occurred during the Libra/Scorpius transition. In contrast, the May 31 Blue Moon occurs deep in the Scorpius constellation, right next to its brightest star, Antares.

For those searching for Sagittarius blue moon astrology meanings, a brief clarification is necessary. While astrological charts place this Blue Moon in Sagittarius, astronomically, the Moon is physically located in Scorpius before moving into Ophiuchus. We focus strictly on the astronomical reality of the event, but we recognize this is a common point of confusion for skywatchers.

Understanding the shift: The astrological zodiac does not perfectly align with the astronomical constellations due to the precession of the equinoxes over thousands of years. Therefore, when observing the smallest full moon of 2026, you will clearly see it positioned within Scorpius.

When is the Next Blue Moon After May 2026?

Wondering about the next blue moon after May 2026? Per EarthSky's explicit enumeration of the 8 calendar-month Blue Moons in the current 19-year Metonic cycle, the next seasonal Blue Moon occurs on May 20, 2027. According to EarthSky, "The next seasonal Blue Moon on May 20, 2027, happens because June's full moon falls about two days before the June solstice."

The next monthly Blue Moon will fall on December 31, 2028. It is also worth noting that there are no Blue Moons at all in the year 2030, making the blue moon 2026 event one you won't want to miss.

Related Zendar Universe updates:

• Eta Aquariid meteor shower – Catch up on the remnants of Halley's Comet.
• 2026 planetary parade – Don't miss this spectacular multi-planet alignment.
• Asteroid 2026 JH2 flyby – Review our coverage of the recent near-Earth asteroid.

Frequently Asked Questions

Review our comprehensive FAQ below for quick answers about the May 31, 2026 Blue Moon, Antares occultation, and local viewing times.

Make sure to check back on May 31 as we update this post with live images from the Antares occultation! We will continue to track the smallest full moon of 2026 as it traverses the night sky.