What are shooting stars and how to see them

Among the most fascinating shows that the night sky can give us, there are undoubtedly shooting stars. A phenomenon that returns to surprise us cyclically, making us raise our eyes to the sky several times a year. Phenomenon that happens every time the Earth crosses dense swarms of rocky debris and ice scattered in our solar system. The particular brightness then performs the rest of the magic, experienced by most during the summer, on the night of San Lorenzo. This is certainly the most propitious period, but it is also possible to admire them during other seasons.

Of course, it is not always easy: the weather must be favorable, it is necessary to look for a not too illuminated place, far from the light pollution of the inhabited centers. Impatient to find the right opportunity to see the next shower of stars, later we will discover together all you need to know to "seize the moment".

What are shooting stars

The peculiar visibility of shooting stars is mainly due to their brightness, which indicates a greater proximity to the atmosphere of our planet. In reality it is wrong to speak of shooting stars: those that we indicate with such a dreamlike description, are actually swarms of debris that wander in space and that, coming into contact with the Earth's atmosphere, overheat and burn while they are crossing it. They give rise to visible radiation, which appear to viewers on Earth as magnificent light trails.

They do not actually crash to the ground, indeed, they do not even touch it!, but they appear more exactly as meteor fragments, called meteorites, which become visible to the naked eye when they come into contact with the Earth's orbit. The proximity to the Sun and the friction due to this contact, triggers a rise in temperature that can exceed 1600 degrees Celsius. It is at the moment when they become luminescent that stars deplete all the elements of which they are composed, such as ice, carbon dioxide and methane. This is precisely why we can only see them glowing for a few seconds, depending on the size of the space debris.

Space debris is also usually carried by comets and, as mentioned above, can be as large as rocks or, much more often, as grains of sand. They derive from fragments of comets, asteroids, or other celestial bodies. In case of limited size, as happens for shooting stars, the scientific community calls them meteoroids until they travel in space, meteors when they enter the Earth's atmosphere, and finally meteorites when they touch the Earth. Occasionally you can also observe bolides, especially when the light trail generated is much more intense than that of other stars. Be careful, however, not to confuse them with the much more dangerous asteroids, with a potentially catastrophic impact on the balance of our planet.

The magic of meteors

When you see shooting stars to mark the sky, we are actually observing a meteor that, at the very high speed of 215 thousand kilometers per hour, is making its ephemeral descent. Depending on the type of swarm and the direction of its orbit, shooting stars can travel between 10 and 7 km per second, heating up for very brief moments. The process that takes place when the debris is overheated on contact with the Earth's orbit is that of sublimation, while subsequently continue to burn thanks to the friction created, following the principle of ablation. At this point, in fact, the meteor is completely enveloped by ionized gases that form a very long tail composed of plasma.

The color of this tail can vary depending on the chemical composition of the rock fragment that sublimate, obviously characterized by different elements. Looking up, we will notice tones of yellow if iron is the main component, notes of yellow-orange if it is sodium, shades of green-blue for magnesium, while an intense red when in the space debris are nitrogen and oxygen to be the masters. It seems indisputable that to speak of magic is not an exaggeration, for what is one of the most beautiful natural shows that the sky can offer. And that, sharpening the view, can give a real explosion of colors to be seized on the fly. Immediately after, the meteors shine until completely dissolved or, if large enough, explode hurling tiny fragments that can exceptionally reach the ground.

When you see shooting stars

The daily life so hectic and too often focused on the Earth does not allow us to always realize, but small fragments of rocks wandering in space constantly meet our planet. In the previous paragraphs, however, we pointed out that there are appointments more canonical than others to watch shooting stars cross the sky with their frenetic play of light. Of course, the reference is to certain periods of the year when the visibility is much higher, such as August 10 in the night of San Lorenzo.

The phenomenon always occurs when the Earth encounters on its orbit fragments and dust of comets left behind in their "journey", closer to the Sun and Earth. This happens several times each year, with the orbits of these clusters of debris generating meteor showers that are named after the constellation closest to the radiant, which is the point in the sky from which the shooting stars appear to arrive if observed from our perspective.

In San Lorenzo, for example, shooting stars are named after the constellation of Perseus. In reality, the passage of the Perseids encompasses an even more extended period, running from late July through August, with a peak between August 9 and 13 each year. Not only that, the arrival of the Perseids, which can be seen by orienting towards the northeast, is a phenomenon known since ancient times. Not surprisingly, during the Roman Empire their passage coincided with the festivities dedicated to Priapus, the god of fertility: the shooting stars were considered the sperm of the god who fertilized the earth.

Today, scholars, and we as a reflection, know that the Perseids are debris that was left behind by the comet Swift-Tuttle, which on occasion has been found to pass close to our solar system. The comet was discovered for the first time in 1862 by the Italian astronomer Giovanni Schiaparelli, and for each passage it is unfortunately necessary to wait hundreds of years: the last time was in 1992, while the next will fall only in 2126.

As previously explained, the one in August is not the only appointment for lovers of shooting stars. At the beginning of the year, and more precisely between the first and the 6th of January, with a peak on the 3rd of the month, there is in fact the arrival of the so-called Quarantids, which originate in the constellation of Boote and are linked to the fragments of a comet, called C/1490 Y1, already known half a millennium ago by Japanese and Chinese astronomers. Jumping to April, between day 19 and 24, the sky lights up thanks to the passage of the Lyrids, so called because they come from an area of the cosmos that is located between the constellation Lyra and Leo, in a northeast direction. The occasion is offered also in this case by the passage of the comet C/1861 Thatcher, fixed every 415 years near our Earth. The last one took place more than 30 years ago, in 1982.

Still, between May 1 and May 8, the Aquarid Aeta, linked to the constellation Aquarius and debris from the famous Halley's comet, are to be remembered. Also between mid-July and mid-August, together with the Perseids, the shooting stars called Delta Aquarids can be observed, also from the constellation Aquarius. From October 16 to 30 is then the turn of the swarm known as Orionidi, fragments of the star Betelgeuse and coming from the constellation of Orion. Until the end of November, the Orionids travel side by side with the Taurids, coming from the constellation Taurus, and the Leonids. The Geminids, on the other hand, are visible between December 7 and December 20, and are observed as fragments of asteroid 3200 Phaethon, passing through the constellation Gemini of course.

How to Take Pictures of Shooting Stars

Now that we know when shooting stars are seen, we might want to take pictures of such a spectacle to share with others. Unfortunately, due to their so ephemeral nature, they are impossible to capture on screen using a simple smartphone. In order to photograph the passage, it is therefore absolutely necessary to arm yourself with a camera, which with the help of a tripod should be placed in a dark place, as far as possible from sources of light pollution and diffuse lights, especially if artificial. According to the advices of the most experts, the diaphragm must be opened to the maximum of its extension, the exposure times must be long, while the ISO sensitivity must be rather high to avoid that the image is ruined by annoying noise. At this point all we have to do is point towards the radiant, the point from which the shooting stars we want to immortalize forever come from, and finally focus. Do not forget to make a wish, a tradition still very strong and ancient origins.