Rare ‘blue moon’ appears tonight—but you may be disappointed | Science | News
Stargazers across the country will witness the so-called “Blue Moon”; But astronomers warn that it won’t live up to the colorful name many were expecting. According to Evan Irawan Akbar, a lecturer in the Astronomy Research Group of Bandung Institute of Technology (ITB), the Blue Moon is not a celestial event that turns the Moon blue.
Instead, it refers to the second full moon occurring within the same Gregorian calendar month. In May 2026, the first full moon occurred on May 2, and Sunday night became the second full moon and therefore the Blue Moon.
Mr. Akbar emphasized that the Moon will look like an ordinary full moon tonight. It will not appear larger, brighter or bluer in color.
He added: “The May 31 event has nothing to do with the Moon turning blue. The Moon will look like a normal full Moon again.”
The term “Blue Moon” originates from traditional American naming conventions for full moons tied to seasons or events (such as “strawberry moon” or “harvest moon”). Its modern usage as the second full moon in a month became popular after it was misinterpreted by James Hugh Pruett in his article in Sky & Telescope magazine.
True blue moons are rare and irrelevant. They can form due to atmospheric conditions, such as when large particles from volcanic eruptions scatter light.
A notable example was the 1883 Krakatau eruption, where observers in Europe reported bluish moons and unusual sunsets.
Unlike the saying “once in a blue moon,” which denotes rarity, Blue Moons are relatively common astronomically.
They occur approximately seven times every 19 years and can fall in any month due to the Moon’s synodic period of approximately 29.5 days compared to the Gregorian months of 30 or 31 days.
Future Blue Moons are projected to occur on December 31, 2028 and September 30, 2031.
For observers in the UK, the full moon reaches its peak at around 9:44am British Summer Time. However, the Moon will remain visible throughout the night, rising near sunset and setting the next morning. No special equipment or telescope is needed; can be observed with the naked eye.
ITB’s Astronomy program, which operates facilities such as the telescope laboratory and Bosscha Observatory on the Ganesha Campus, is not conducting special observations for this event as it lacks unique scientific phenomena beyond calendar definition.
Mr. Akbar noted that public interest in the Blue Moon provides a good opportunity to educate people about lunar cycles and the calendar system.
So, while tonight’s “Blue Moon” offers a beautiful full moon to enjoy, those hoping for a truly blue moon view may indeed be disappointed.
