Astronomical events known as a blue moon and a micromoon will coincide on Sunday, May 31, creating a "blue micromoon" visible across Australia. The event is a combination of two separate lunar phenomena occurring simultaneously.
Definition and Key Characteristics
The term "blue moon" in this context refers to the second full moon occurring within a single calendar month. The first full moon in May took place earlier in the month.
A "micromoon" occurs when a full moon coincides with the moon's apogee, the point in its orbit farthest from Earth. According to reports, the moon will be approximately 406,000 kilometers from Earth at this time.
Despite the name "blue moon," the moon will not appear blue in color. Its size will be noticeably different from a standard full moon. One source states the moon will appear approximately 6% smaller than an average full moon, while another reports it will appear approximately 14% smaller and 30% dimmer. This size difference is generally not noticeable to the naked eye.
Viewing Times and Visibility
The moon is expected to reach peak fullness at approximately:
- 6:45 PM AEST (New South Wales)
- 6:30 PM local time (Sydney, Melbourne, Brisbane, Canberra)
- 6:00 PM local time (Adelaide, Darwin)
- 4:30 PM local time (Perth)
The moon will appear full throughout the evening and most of the night. Astronomer Laura Driessen described the moon as "tens of thousands of times brighter than the brightest star." Sources recommend viewing shortly after moonrise, when the moon may appear larger due to the "moon illusion" and may take on golden, orange, or reddish hues due to atmospheric effects. In New South Wales, the moon will rise in the southeast and travel low across the southern sky.
Viewing Recommendations
The event is visible from any location in Australia with a clear view of the night sky and minimal cloud cover. To optimize viewing, sources suggest:
- Darker locations away from light pollution
- Open areas such as parks or beaches
- An unobstructed view of the southern horizon
Specific recommended locations in Sydney include:
- The Bondi to Coogee coastline
- Observatory Hill
- Barangaroo Reserve
No special equipment is required, though binoculars or telescopes can enhance detail. The moon is visible to the naked eye. Viewers are advised to check local weather forecasts and to ensure proper lighting and awareness of surroundings when viewing at night.
Scientific Context
Dr. Michael Brown, an Australian astronomer, stated that the alignment is coincidental and not considered scientifically significant, though it is visually interesting.
According to forecasts, the next similar alignment may occur in December 2066.