Blue micromoon to grace Chennai

Chennai: A rare Blue Moon will illuminate the city skies on Sunday night, offering residents a chance to witness an unusual celestial event that combines a Blue Moon with a micromoon, also called a minimoon.

Experts said despite its name, the Moon will not appear blue. A Blue Moon refers to the second full moon occurring within the same calendar month, a quirk caused by the mismatch between the Moon’s 29.5-day lunar cycle and the calendar month. Since most months have only one full moon, Blue Moons occur only once every two to three years, giving rise to the phrase ‘once in a blue moon’.

What makes Sunday’s event more unusual is that it is also a micromoon, meaning the full moon occurs near apogee, the Moon’s farthest point from Earth, at about 4,05,500km (closest distance is 3,63,300km). As a result, it may appear slightly smaller and dimmer than usual.

“The Moon will appear in the eastern sky after sunset on May 31. Although it may look smaller and dimmer, most people may not notice the difference,” said S Soundararaja Perumal, former executive director of Birla Planetarium.

While micromoons occur several times a year, astronomers consider their coincidence with a Blue Moon uncommon. The city last witnessed a Blue Moon in August 2023, while experts suggest a similar Blue Micromoon combination may not recur for decades, though dates vary depending on time zones.

Residents can view the Moon shortly after sunset from terraces, beaches, parks and lakesides with an unobstructed eastern horizon. No telescope is needed. Smartphone users can improve photographs by tapping to focus, lowering exposure and including foreground elements such as buildings or trees for scale.