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If you’re still daydreaming about the April 8 total solar eclipse, dazzling auroras or last month’s Eta Aquarid meteor shower, you’re in luck: Another rare celestial spectacle is happening now.
Called a “major lunar standstill,” this natural phenomenon only occurs every 18.6 years. The standstill is not just one day, but a period of about two years when the moon rises and sets at more northerly and southerly spots along the horizon than normal. In addition, from our perspective on Earth, the moon will appear to reach its highest and lowest altitudes during this time.
The major lunar standstill will peak in January 2025. But it can be seen through the middle of next year.
“Throughout the roughly two-year standstill ‘season,’ the moon will rise at the northernmost and southernmost extreme every 27 days,” Fabio Silva, an archaeologist at Bournemouth University in England, tells Smithsonian magazine in an email. “But this will occur at different phases of the moon, not all of which will be visible or dramatic. It is on or very close to the solstices that this will coincide with a full moon, making for very dramatic displays.”
On Friday, just one day after the solstice, the full moon is expected to offer some of the most extreme views of the lunar phenomenon—it will rise and set at its southernmost points, and it will travel very low across the sky.
“In locations with high hills/mountains in the south, the moon may not be visible at all, appear only for a brief period of time or, if the conditions are right, the moon may appear to be rolling across the hills (simply due to the fact that it will be very low in the sky),” Silva adds.
If you’d rather stay indoors, you can watch a live stream of the southernmost moonrise at Stonehenge, which—provided the weather holds out—should be a stunning sight. Researchers in England are spending the next year studying whether the major lunar standstill may have influenced the design of the monument.
Here’s your guide to the unusual lunar event.
What is a major lunar standstill?
Every day, the moon rises in the east and sets in the west. But the location of the moonrise and moonset on the horizon changes, moving from north to south to north again over the course of a month. Throughout the 18.6-year lunar cycle, the northernmost and southernmost extremes also change.
During a major lunar standstill, the northernmost and southernmost moonrise and moonset are at their farthest distance apart. As such, this affects how long the moon appears to stay in the sky.
This phenomenon occurs because of the tilt of the Earth on its axis as it orbits the sun, as well as the tilt of the moon’s orbit around the Earth. The moon can rise and set within a 57-degree range over the course of a month, while the sun rises and sets within a 47-degree range over the course of the year. This means that at times, the moon can appear to rise and set at more northerly and southerly spots along the horizon compared to the sun.
The moon in archaeology
To the casual observer, the northern and southern fluctuations of the moonrise and moonset may be hard to notice. But for individuals who watch the sky closely—including many ancient cultures—it’s more obvious. During times when the moon rises and sets outside the sun’s range in the sky, ancient people may have noticed—and imbued those periods with meaning.
“A moon-watcher would have seen the moon start to rise or set outside of these limits, moving farther and farther out of bounds as the major lunar standstill approached,” says Erica Ellingson, an emeritus astrophysicist at the University of Colorado Boulder who is studying a possible connection between the major lunar standstill and Chimney Rock in Colorado, to CNN’s Katie Hunt.
Archaeologists on Friday will be watching how the moon appears over Stonehenge, which has a recognized connection to the sun. But now, Silva and otherresearchers are probing whether the monument’s construction was also linked to the moon. It seems that four boulders around Stonehenge, known as Station Stones, are aligned with the moon’s northernmost and southernmost rises and sets.
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The researchers have been observing the moon’s extremes from Stonehenge this year, but according to Silva, the weather has often gotten in the way. Friday’s full moon offers the next major opportunity for the project.
“We’ve had opportunities twice [a] month since February, but we’ve only managed to observe it three times because of the weather,” Silva says. “If we do manage to observe it [on Friday], we are interested in recoding where and when it will first appear, how it will be framed by the stone circle as it moves across the sky and assess whether the alignment of Station Stones and major standstill moon was intentional or merely a coincidence.”
Summer solstice, strawberry moon
This month’s full moon is called the strawberry moon. It will rise in the sky one day after the Northern Hemisphere’s summer solstice, which occurs on June 20 at 4:51 p.m. Eastern time—the earliest of any summer solstice since 1796. This marks the longest day of the year and occurs because the Earth’s northern pole is tilted toward the sun at its most extreme angle.
When the full moon rises on Friday, it will appear very low in the sky. This could make it look huge to Earth-bound observers, thanks to what’s known as the “moon illusion.” In places at high latitudes, the moon will be so low it may not even be visible above the horizon, according to the Farmer’s Almanac. The moon may also take on an orangish-pinkish hue, because of the way light passes through Earth’s atmosphere.
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Sarah Kuta | READ MORE
Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.
