A rare blue micromoon arrives this weekend and won’t be back until December 2028. Here’s what to expect. A blue micromoon, defined as the second full moon in a single month and the year’s most distant and smallest full moon, will be visible this weekend. While not visually blue, it occurs once every two to three years. This event, the opposite of a supermoon, will be approximately 6% smaller and 10% dimmer than an average full moon, with subtle differences potentially going unnoticed by many observers.

• A blue micromoon occurs when there are two full moons in one month, with the second being the most distant and smallest-looking of the year.
• This celestial event happens roughly every two to three years, with the next one not expected until December 31, 2028.
• The moon will appear about 6% smaller and 10% dimmer than an average full moon, with subtle differences noticeable only to keen observers.
• In the Northern Hemisphere, the blue micromoon will be seen alongside Antares, a bright star in the constellation Scorpius.
• Skywatchers south of the equator and across the Pacific may witness the moon obscuring Antares.
• The Virtual Telescope Project will stream live images of the blue micromoon.