15 Strange Phenomena in the Sky

Unusual rainbows, bright sprites of red light, and halos from the heavens. Here are the top 15 strangest sky phenomenon. Number 15. Fire rainbow. Fire rainbows, which are also known as circumhorizontal arcs, are a phenomenon that occurs when sun or moonlight is refracted through specifically shaped ice crystals within cirrus or cirrostratus clouds. It's something that you have a good chance of seeing in the US during the summer each year. But while the arc is often referred to as a rainbow, it's not actually a rainbow at all. The strange halos are formed when light enters the vertical side face of a flat hexagonal ice crystal that's horizontally oriented and exits along the bottom face. Because the ray is refracted almost 90 degrees, the colors are clearly separated. And while you may see a fragment of a fire rainbow quite regularly, the chances of seeing a fully formed halo are much more remote. The actual light that's formed will take on a perfectly circular shape, but it's the presence of the clouds that will often make these arcs seem wispy, almost like flames lapping in the sky. To take place, not only does there need to be the right type of ice-forming clouds in the sky, but the Sun has to be very high, at more than 58 degrees, which means that it's impossible to see the solar versions of them at locations north of 55 degrees north or south of 55 degrees south. Los Angeles is one of the best places to witness this phenomenon, because the Sun is higher than 58 degrees for 670 hours each year between March and September. So if you ever want to see one for yourself, that's the place to go. Number 14. Red Sprites. From the ground, we're used to seeing bright flashes of light in the sky during thunderstorms. Further up beyond the clouds that form these bolts, there's an even stranger electrical phenomenon called a red sprite. Thought to be triggered by the formation of light between a lower cloud and the ground, they occur at altitudes between 31 and 56 miles, and often appear in clusters of reddish-orange flashes. While they may themselves look like lightning, red sprites are actually formed by cold plasma, which means the process that creates the flashes is much more similar to the production of light inside a fluorescent tube. Immediately prior to a sprite formation, a red halo can be seen, and when there's a massive thunderstorm below, they may also form blue tendrils that reach down. It's extremely difficult to see them from ground level, however, and some of the best images have been taken from space. Because of this, very little is known about the actual conditions inside a red sprite, but several high-altitude aircraft and balloons are thought to have been severely damaged by them, so they're almost certainly more powerful than the lightning we're more familiar with. Number 13. Sun Halo. As the name would suggest, a sun halo is an atmospheric phenomenon that leads to the formation of a halo of light that surrounds the sun in the sky. There are a number of ways that they can form, but normally it's the result of the presence of ice crystals that are suspended in the atmosphere inside cirrus or cirrostratus clouds. The most famous type is known as the 22-degree halo, which looks like a ring around the sun and has a radius of 22 degrees. It's formed when the light bounces off virtually randomly arranged ice crystals. But crucially, they don't reflect any of the light back towards the sun. This results in the sky within the halo being noticeably darker than the sky that surrounds it, and it's often misidentified as a mysterious hole forming in the heavens. Number 12. Noctilucent Clouds. Noctilucent clouds, which translate from Latin to mean night shining, are some of the highest forming clouds in the atmosphere and take on a very strange appearance during twilight. Existing at between 47 and 53 miles high, very little is known about them, and because they're so thin and transparent, it's almost impossible to see them during the day. And the reason they become visible after the sun is set is because of the curvature of the earth. It's only possible to see them during the summer at locations that are between 50 and 70 degrees north and south of the equator. Once the sun is lowered beneath the horizon, the light still illuminates these clouds that are high up in the atmosphere, while the lower layers of the atmosphere are darkened by the earth's shadow, and means they stand out. This makes them very difficult to study, and researchers still aren't sure why they form. They appear to be linked with pollution levels and large-scale changes in the upper atmosphere. The record suggests that their frequency and brightness have been increasing in recent years. Number 11. Zodiacal Light. We're used to the world being illuminated by the sun and the moon, but there's a phenomenon called zodiacal light that's created by dust in space, often known as the false dawn. The chances are that you've actually seen this in real life, as it's a triangular-shaped light that appears in the sky following sunset or just before the sun rises. Surrounding our planet and throughout the solar system is a pancake-shaped collection of dust known as the zodiacal cloud, which has been formed by debris left behind by comets. When it's at the optimal angle in relation to the earth and the sun, it will reflect the sun's light back onto the dark side, although light pollution and a full moon will overwhelm the zodiacal light and make it invisible. It's a phenomenon that has been observed for centuries, with some of the first astronomers writing about it and trying to understand its causes. And amazingly, it was Cassini who first proposed it was the result of dust particles, having deduced the cause with his relatively primitive apparatus in 1683. Number 10. Fall Streak Hole. Fall streak holes are one of the strangest sky phenomena you'll ever see, and have long been associated with powerful gods, trans-dimensional beings, or aliens because they look so much like a portal to another world. Forming in cirrocumulus or altocumulus clouds, they appear as a large gap, usually circular, within the otherwise blanketed sky. There's actually a complicated process behind their formation, and they occur when the temperature of the water in the clouds is below freezing, but the water itself has entered a supercooled state where ice crystals haven't yet begun to form. When they do finally begin to take shape, an effect called the Bergeron process takes place whereby the water droplets around the ice crystals actually begin to evaporate and therefore leave an empty patch of sky where the clouds once were. The introduction of ice crystals into a region where this is happening can speed up the process, and they're often associated with planes that have flown through the clouds and done this. Number 9. Crepuscular Rays. Crepuscular rays, which are more commonly known as god's rays, are a specific type of sunbeam that can often be seen shining through the gaps in clouds or through permanent objects like mountains or buildings. Quite often they appear to radiate from where the sun is, but surprisingly this is actually an optical illusion, and they are instead parallel to one another. Sometimes they can stretch across the entire sky and appear to meet again at the other side, but this happens because of perspective. The rays form during twilight when the sun is below the horizon and become more apparent as the sky gets darker because of the contrast between the light and the dark. They're orange in color because the light's path through the atmosphere sees it travel through up to 40 times as much air as midday rays, which gives more opportunity to refract its wavelength. We're constantly adding more people to the Top 5's production team to bring you all the best content. Be sure to subscribe with notifications on and hit the like button. Number eight, mammatus clouds. Mammatus clouds are an unusual type of cloud formation that look like pouches hanging beneath other clouds, hence the reason why they were given the latin name mama, which means utter. They aren't actually classified as a cloud in their own right, but instead a supplementary feature that sometimes occurs on other clouds, usually a cumulonimbus rain cloud. If you ever see them forming, it's usually a sign that a powerful storm is on its way, so much so that pilots are taught to avoid them at all costs. They look like smooth lobes protruding from beneath a parent cloud, and each one can be up to two miles across, but the exact means of their formation is not fully understood. It's thought to be linked to sharp variations in temperature, moisture, and wind speeds, which cause water droplets to cool, fall, and then reheat again, all while being contained by circular wind patterns. There are, though, several different theories, including the influence of gravitational waves, cloud melting, and thermal reorganization, showing that the scientific community is by no means aligned on precisely why mammatus clouds happen. Number seven, the Belt of Venus. Just before the sun rises in the morning, or just after it is set at night, you might see a strange atmospheric phenomenon called the Belt of Venus. It forms in the opposite direction to where the sun is, and creates a pinkish glow in the sky that rises above the horizon due to the backscatter of reddened sunlight, known as Rayleigh scattering. In the evening, as time progresses, the Earth's shadow rises from the horizon, and the Belt of Venus rises even higher into the sky as it bounces off the fine particles in the atmosphere, before dissipating. During different times of the year, the color of the effect can change between a vivid pink to a reddish orange, and it's a similar process to the one you see when the moon has a red hue. The hazy light gets its name because, due to its position in the sky, at no point will the planet Venus ever appear within the phenomenon, and so the two were historically thought to be linked. Normally, we think of lightning as either illuminating the entire sky without any definitive position, or shooting down on a bolt towards a specific point on the ground. There is, however, another way in which it can form, and it's far more unpredictable than its counterparts, to such an extent that it's not entirely certain that it exists or not. Known as ball lightning, it's thought to be an electrical phenomenon that sees a spherical ball of luminescence that can range from the size of a pea to many feet in diameter. Sightings have usually been during thunderstorms, but ball lightning is said to last a lot longer than the split-second lifespan of a bolt. There have been a number of accounts of ball lightning throughout history, including those claiming that it occurred at ground level and left a smell of sulfur behind. It's been possible to create it in a laboratory condition, too, but examples of it happening naturally are incredibly rare. Number five, pyrocumulus cloud. Pyrocumulus clouds, which are often also called fire clouds or phlegmogenitus, are ones that often form near volcanic eruptions or widespread fires. The air at the surface becomes incredibly hot, so begins to rise and eventually settles at a point of stability in the atmosphere, which is usually where there's a dense region of moisture. This then condenses to create a huge cloud formation, one that's associated with extreme turbulence and, on occasions, the production of dry lightning. The presence of ash from the preceding fire means that the clouds are usually gray in color and are able to trigger thunderstorms, which can either be a blessing or a curse. The rain can help to extinguish the fire that's caused it, but if there's enough lightning, there's a chance that further fires can be started if it happens to strike a region of dry vegetation. Number four, morning glory clouds. So-called morning glory clouds are a rare phenomenon. They're a band of long roll clouds, sometimes more than 600 miles long and more than a mile high, form relatively close to the ground. There may be one of the clouds on its own or as many as 10 alongside each other, and when they form, there's usually unpredictable surrounding winds that make them extremely popular for glider pilots. The clouds can travel at up to 65 feet a second and form new growth on the crest while dissipating at the rear. There are very few places in the world where they occur, and there's only one location where they are foreseeable and often develop. The southern region of the Gulf of Carpentaria on the northern coast of Australia. Here, because of the unique geography of the land and sea, a few form every year and have been documented ever since 1942. Due to their rarity, their formation isn't fully understood despite several research projects, but it's believed to be related to a very precise balance of wind direction, moisture, and atmospheric pressure. Similar formations are occasionally seen in the U.S., Europe, and Russia, but in no way as predictable a fashion as in Australia. Number three, crown flash. A crown flash is an incredibly rare phenomenon that looks like a powerful searchlight moving around in the sky. They're so unusual that they're often interpreted as being mystical, and those who see them tend to report a spiritual experience. Commonality between all sightings is that there's a brightened crown of a cloud followed by an aurora-like streamer that bursts out towards the sky. But the rate at which the direction of the light beams move is almost unbelievable. As they're very uncommon, there's little research into their formation, but researchers believe they understand in theory the causes. It's all to do with the arrangement of ice crystals within cumulonimbus clouds. They're surrounded by powerful electromagnetic effects that orient the crystals in the same direction. And when sunlight shines into them, it's refracted away and appears like a beaming light. For some reason, however, the direction of the electromagnetic field can rapidly change, likely due to discharges like lightning flashes within the cloud. This causes the ice crystals to instantly move into an alternative orientation. This changes the direction that the beam of light is shining in a fraction of a second, and can result in the light seeming to dance across the sky in a mechanical way. To see one, you have to be at precisely the right position to see the refraction of the light, because the beam isn't being generated from within the cloud. Which means that if you're ever lucky enough to witness a crown flash, you should stay and watch the show, because very few others have ever been able to. Number two, lenticular clouds. A lenticular cloud is a large type of stationary cloud that form at altitudes of up to 40,000 feet, and take on a peculiar saucer-shaped form. They're formed when wind blowing across the land encounters large obstacles, and the results can be spectacular. Mountains, volcanoes, and even large buildings will severely disrupt the way that wind can flow through a region, and produces eddies in a similar way to what happens to water in a river. When this happens, and if the warmer air that contains water droplets flows over the eddy, the moisture can begin to condense and start to form a cloud. The circular nature of an eddy is why lenticular clouds take on such a smooth lens-like shape. And while those that live in mountainous regions may be quite used to seeing them, people who live in flat terrain won't have seen anything like it. It's because of this that lenticular clouds, especially when they form in places where they're less common, are linked with an increased number of UFO sightings, when people become convinced that such a perfect shape can only be the result of an intelligent design, and not simply a weather formation. The winds within them can be extremely turbulent, too, which means that pilots of powered aircraft will actively avoid them. Glider pilots see them as some of the most enjoyable weather systems it's possible to fly into. With such huge uplift of wind at the leading edge of a lenticular cloud, it's possible to reach great heights in a matter of seconds, and has resulted in the gliding records for distance and for height both being set thanks to one. Number one, aurora. The most famous atmospheric phenomenon in the world is the aurora borealis, an effect that occurs close to the earth's north pole where charged particles are ionized and released photons that produce spectacular displays of light in the sky. They're also seen in the Antarctic, too, where they're called the aurora australis, and these light shows are just as incredible, if not a little more difficult to travel to see. The visibility of the aurora are surprisingly predictable, and their appearance can be charted on maps in the same way as the weather is. Typically, they're only visible between 10 and 20 degrees from each pole, and are clearest on a dark night. And the region where you can see them at any given time is known as the aurora oval, because this is an effect that's linked to the magnetism of the earth. However, it is possible to see them much further beyond the usual area when there's a geomagnetic storm. They're also not just limited to the earth and are seen throughout the solar system, particularly on Venus, Mars, Saturn, and Jupiter. Subscribe to Top5s for more and check out some of our other popular videos.