CAPE CANAVERAL, Fla. (AP) — Skywatchers will have a chance to see a rare blue micromoon this weekend as the second full moon of May rises Sunday night.

A blue moon occurs when two full moons fall within the same calendar month, a phenomenon that happens only every two to three years. The first full moon of May occurred on May 1, making Sunday’s full moon the month’s second and earning it the blue moon designation.

The moon will also be a micromoon, meaning it will be at one of its farthest points from Earth during its orbit. According to astronomers, the moon will be about 252,360 miles from Earth, making it appear slightly smaller and dimmer than a typical full moon. By comparison, a recent supermoon was about 225,130 miles away.

Gianluca Masi of the Virtual Telescope Project said the micromoon will appear about 6% smaller and 10% dimmer than an average full moon, though the difference will likely be difficult for most people to notice without careful observation.

The celestial event will offer another treat for stargazers as the bright red star Antares appears next to the moon. Antares, often called the “heart of the scorpion” because of its position in the constellation Scorpius, is a red supergiant star located about 550 light years from Earth.

Observers in parts of the Southern Hemisphere, including Argentina, Chile, New Zealand and eastern Australia, may see the moon briefly pass in front of Antares, causing the star to disappear from view for a short time. Elsewhere around the world, including South Dakota, Antares will remain visible near the moon throughout the night.

Despite its name, a blue moon does not appear blue. The term refers only to the uncommon occurrence of two full moons in a single month.

Weather permitting, the blue micromoon will be visible Sunday evening across the Black Hills and western South Dakota.