Tuesday, August 10, 2021

Tears of San Lorenzo are coming

Like every year, the date is approaching to enjoy the famous meteor showers that will reach their peak this summer of 2021.

Throughout the month of August you will be able to observe the Perseids or tears of San Lorenzo, whose peak of activity is expected for Thursday, August 12.

The Perseid shower is a meteor shower (commonly called "shooting stars") that occurs every year around August 12. The Perseids are also popularly called "Tears of San Lorenzo" due to the proximity of the peak of the meteor shower to August 10, the feast day of the Spanish martyr of the same name.

The Perseids are visible from across the Northern Hemisphere in midsummer. The speeds of these meteors can exceed 50 kilometers per second and their activity rate can reach 200 meteors per hour. Although their peak activity occurs on the nights of August 11-13, the Perseids usually begin to be seen around July 17 and end around August 24. Their high activity, together with the favorable atmospheric conditions for observation during the boreal summer, make the Perseids the most popular meteor shower, and the most easily observable, of those that take place throughout the year.

Comets, as they describe their orbits around the Sun, are throwing into space a trail of gases, dust and debris (rocky materials) that remains in an orbit very similar to that of the parent comet.

Each comet thus forms a ring in which numerous cometary fragments are distributed. When the Earth, in its movement around the Sun, encounters one of these rings, some of the rocky fragments (meteoroids) are trapped by its gravitational field and fall at high speed through the atmosphere forming a meteor shower.

Friction with atmospheric gases calcines and vaporizes meteors that appear bright for a fraction of a second, forming what we popularly call shooting stars. It is therefore not a star but a particle of incandescent dust.

The height at which a meteor becomes bright depends on the speed of penetration into the atmosphere, but it is usually around 100 kilometers.

However, the high brightness and high transverse velocity of some meteors cause a spectacular effect, causing the illusion to the observer that they are very close.

Every year at the beginning of August, our planet crosses the orbit of comet 109P / Swift-Tuttle, which has a period of 133 years and last passed near the Sun in 1992. This orbit is filled with small particles, like grains. sand or smaller, which have been released by the comet in its previous steps. When one of these particles, which once formed the comet's tail, enters the Earth's atmosphere at high speed, friction heats it until it vaporizes at a great height.

The corresponding meteor shower appears to have a single center of origin, a point from which all shooting stars appear to emerge. This point is called "radiant" and its location is used to name the meteor shower. Thus, the Perseids have their radiant in the constellation of Perseus.

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