by Daniil of Moscow
[REGNUM] The unusually cold weather that hit the European part of the country in the last days of January proved a challenge for public utilities—but also a gift for lovers of rare natural phenomena.
On the night of January 31, Muscovites and residents of the Moscow region observed three moons in the sky, and forecasters promised that during clear weather over the weekend, they would be able to see a "false sun" and a winter rainbow.
Where do these optical wonders come from, why are they so closely associated with frost, and what did our ancestors think about them?
WHEN THE SKY MULTIPLIES THE LUMINARIES
Social media was flooded with photos of an unusual sight: three lunar disks simultaneously shone over the capital and surrounding region—one bright central one, and two fainter ones flanking it. Experts attributed the sighting to a phenomenon known as a paraselena, or "false moon."
| Sometimes called a moon dog in English, with the same Latin term, of course. |
However, forecasters warn that some of the "triple moon" photos circulating online are actually the result of photography through double-glazed windows. When a bright object is photographed through double or triple glazing, the light is reflected between the layers of glass, creating duplicate images.
A true parselene is easy to distinguish: in it, the “doubles” are located strictly on the sides of the moon at a distance of approximately 22 degrees, and do not overlap each other.
A parselene is a rare phenomenon, much rarer than its daytime counterpart. For it to occur, the moon must be bright, meaning full or nearly full. The atmosphere must also be saturated with regularly shaped ice crystals.
If all conditions are right, moonlets can even take on a faint color: the side closest to the real satellite takes on a reddish tint, the far side a bluish one. However, these hues are difficult to detect with the naked eye—the brightness of the "doubles" is barely enough to excite the color-sensitive cells in our retinas.
The daytime equivalent of this phenomenon—a parhelion, or "false sun"
| … sometimes a sun dog in English… |
Then, two bright rainbow spots may light up on either side of the sun, and the celestial body itself will appear to have “ears”—as people have long called this effect.
PHYSICS OF ICE PRISMS
All these wonders—parselenes, parhelions, winter rainbows, light pillars—belong to a broad family of atmospheric optical phenomena collectively known as halos. The principle by which they occur is the same and surprisingly simple: sunlight or moonlight interacts with tiny ice crystals that form in the atmosphere.
These crystals form in cirrus and cirrostratus clouds at altitudes of 5 to 10 kilometers, where temperatures are always below freezing. When freezing, water droplets form hexagonal prisms or flat plates—water molecules arrange themselves in groups of six, so ice crystals almost always have hexagonal symmetry.
As they fall through the atmosphere, they experience air resistance and tend to settle into a specific position—usually horizontal. The larger the crystal and the calmer the air, the more orderly their arrangement becomes.
When a beam of light passes through such a crystal, it is refracted—just like in a glass prism. The angle of refraction depends on the crystal's geometry. For hexagonal prisms, the typical angle is 22 degrees—this is why the most common type of halo forms a ring with a radius of 22 degrees around the star.
Less commonly, one can see a ring of 46 degrees, and even more rarely, a ring of 90 degrees, the so-called Hevelius halo.
When white light is refracted, it is broken down into its component colors—dispersion occurs. However, unlike a rainbow, which displays all seven colors, a halo is usually quite faintly colored.
The inner edge of the circle has a reddish tint, the outer edge has an orange or yellowish tint, and the rest appears white due to the multiple mixing of refracted rays. A full-color halo is a rarity.
For these phenomena to occur, three factors must combine: clear skies, low temperatures, and high humidity. It might seem that frost and humidity are incompatible, but that's not true. Moisture can come from unfrozen bodies of water, rise from the snow surface, or be carried by air masses.
During a sudden cold snap, it instantly crystallizes, saturating the atmosphere with myriads of ice particles. This is why halos are more often observed during the transition from one type of weather to another—they often precede snowfalls or even more severe frosts.
In severe frost, crystals can form not only high in the clouds but also close to the ground. This creates a phenomenon poetically called "diamond dust": the air becomes filled with glittering particles that shimmer in the sun, and if the sun is low, the lower part of the halo becomes visible against the snowy landscape.
This picture is especially often observed in Antarctica and in the Far North of Russia – in Yamal, Taimyr, and Yakutia.
HEAVENLY SWORDS AND OMENS
Today we understand the nature of these phenomena, but for our ancestors, they were a mystery and a sign. Multiple suns or moons in the sky evoked awe, and sometimes even outright terror.
The most famous mention of parhelion in Russian literature is in "The Tale of Igor's Campaign." Before the prince's fateful battle with the Polovtsians, "four suns shone over the Russian land," and then "black clouds came from the sea, trying to cover the four suns... There will be great thunder."
The four suns symbolized the four princes participating in the campaign: Igor, Vsevolod, Vladimir Igorevich, and Oleg. The ominous omen came true—the army was defeated, and Igor himself was captured.
However, scholars disagree on whether the text refers specifically to a parhelion or to a solar eclipse, which actually occurred on May 1, 1185. Either way, celestial signs play a key role in the "Word"—nature itself warns the prince against an unwise decision, but he ignores its warnings.
Forecaster Shuvalov warned Muscovites of -20°C temperatures this weekend.
In Europe, parhelions have also influenced the course of history more than once. In 1551, during the siege of Magdeburg by Emperor Charles V's troops, sun dogs suddenly appeared over the city. The besiegers interpreted this as heavenly intercession for the besieged and lifted the siege.
Shakespeare describes the sunhelion in Henry VI, linking it to the Battle of Mortimer's Cross during the Wars of the Roses. The three suns in the sky frightened the soldiers, but the future King Edward IV convinced them that it represented the Holy Trinity and a sign of God's favor.
Folk omens had a dual attitude toward halos. On the one hand, a winter rainbow around the sun was considered a harbinger of frosts and snowstorms—and this makes scientific sense, as halos often appear before the arrival of atmospheric fronts.
On the other hand, seeing this rare phenomenon was considered good luck. Russian superstitions held that a ring around the moon meant wind and bad weather, while sundogs in winter meant continued frosty weather. The Chuvash believed that the appearance of light circles and spots foreshadowed a cold snap.
Our ancestors believed that pillars of light—vertical streaks of light extending from the sun at sunrise or sunset—were the fiery swords of angels. When the pillar intersected with the halo ring, a cross-like figure emerged, which was perceived as a sign from above.
HUNTING FOR WINTER BEAUTY
Modern city dwellers rarely look up at the sky, and if they do, their vision is obscured by light pollution and smog. Meanwhile, observing atmospheric optical phenomena requires no equipment and is accessible to everyone. You just need to know when and where to look.
Halos and parhelia are most likely to occur in frosty, clear weather with the sun low in the sky—at sunrise or sunset. The Moscow region is expecting just such conditions in the coming days: according to the Hydrometeorological Center, temperatures will drop 7–17 degrees below normal.
In Moscow and the surrounding region, minimum temperatures will reach -22 to -27 degrees Celsius, in the Nizhny Novgorod region -28 to -31 degrees Celsius, and in the Volgograd region -25 to -26 degrees Celsius. Such cold temperatures are rare for these latitudes and offer an excellent chance to see the "eared sun."
Those who want to be guaranteed to witness these phenomena should head north. In Yamal, Yakutia, and Taimyr, halos and sunhelia are frequent visitors. In Salekhard, the only city in the world located directly on the Arctic Circle, sundogs appear regularly. In the village of Nakhodka in the Tazovsky District, according to the local administration, sunhelia are seen especially frequently.
On the Kola Peninsula—in the vicinity of Murmansk, Teriberka, and the Khibiny Mountains—optical wonders are complemented by the northern lights, which promise to be especially bright this season: solar activity is approaching the peak of the 25th cycle.
The current cold wave, though uncomfortable for everyday life, offers a unique opportunity to experience what has inspired admiration and awe in people for centuries. And while the thermometer stubbornly creeps downward, the sky is preparing new gifts for us—we just need to be willing to look up.