Rare Blue Moon Hides Ancient Star

People in the southern hemisphere will see a rare sky event on May 31. A Blue Moon will pass in front of Antares. Antares is a very old and bright red star. This movement will block the star’s light for a short time. The event happens just before the moon reaches its fullest brightness. This alignment is a special treat for night sky watchers.

A Blue Moon is not actually blue. The name is just a label for a timing rule. It usually means the second full moon in one calendar month. This happens about once every two and a half years. Sometimes, it means the third full moon in a season with four. The moon does not change color. It stays its usual white or yellow shade. The name only tells us when the moon is full.

People in Australia, New Zealand, and South America will see the best view. The Blue Moon rises on May 31 as the sun sets. Antares will appear near the lower right of the moon. The moon moves across the sky during the night. It will pass directly in front of the red star. Astronomers call this hiding an occultation. A larger object blocks a smaller one from view.

Observers in North America will see a different view. On May 30, the moon and star will be close together. Antares will be about three degrees away from the moon. You can hold up three fingers at arm’s length. This width equals about three degrees in the sky. The objects will move together until they set. However, the moon will not hide the star for these viewers.