Shooting stars in summer (the Perseids)Le Binh San PhamThe maximum activity of the Perseids meteor shower usually occurs around August 11 or 12. Meteors (or shooting stars) can then be observed throughout the night, as well as during the previous and subsequent nights, preferably in the second part of the night, when the Moon is down and the Perseus constellation is high enough in the sky. Meteors seem to come from the constellation of Perseus - hence their name - but this is only a perspective effect. Meteors are luminous phenomena that result from the passage of a solid body from space through the Earth's atmosphere. These are actually dust corpuscles associated with the Swift-Tuttle comet's passage through its orbit. Every year, around August 11 or 12, the Earth passes through this orbit and dust particles left by this comet enter the Earth's atmosphere. These dusts are usually no larger than grains of sand entering our own atmosphere at high speed (up to 60 km/s). They leave bright trails in their path before disintegrating completely before they can reach the ground of our planet. These luminous trails can be observed everywhere in the sky but seem to come preferentially from the constellation of Perseus, which is then above the northeast horizon. In areas with very high light pollution, only the brightest meteors can be observed. In regions with relatively dark skies, up to one meteor per minute can be counted on average during periods of maximum swarm activity. The period of the normal maximum is actually very long in time (over several weeks) because the dust particles have been dispersed for thousands of years in their orbit. This is why it is possible to observe many meteors over a fairly long period stretching before and after the period of the theoretical maximum.
What is een shooting star (meteor)?Le Binh San PhamA meteor or shooting star is caused by a particle that enters the Earth's atmosphere from space. The particle is sometimes called meteoroid. Through the interaction with the atmosphere, light and heat are released and a so-called ionization trail is formed (from 100km of altitude). This is visible as the "tail" of the shooting star. The particle almost always evaporates or pulverises in the high atmosphere (above 20-50 km altitude). Most particles that give rise to meteors are not larger than a few milimeters. A clear meteor, also known as a fireball or a racing car, is a particle that is larger (several centimmeter or more). Often the fireball comes to its end at an altitude of 10 to 20 km. Sometimes this is accompanied by an explosion (without sound) and one also sees different colors. The larger the particle, the brighter the fireball, but also the speed (typically between 10 and 70 km/s) and the composition play a role. Sometimes sounds (pops) are heard during the passage in the atmosphere. Only very rarely does a residue end up on the Earth's surface. That is called a meteorite. There are many species, but they are very rare.