The maximum activity of the Perseids is scheduled for this Thursday, August 12 between 9:00 p.m. and 12:00 p.m. (official hours in the Peninsula). Therefore, the best time to observe the Perseids will be the night of August 12-13, once the sky is dark, after the crescent moon sets over the horizon.
The Perseids, also known by the popular name of “Tears of San Lorenzo” due to the proximity of the maximum of the meteor shower to August 10, the day of the feast of the Spanish martyr of the same name, occur every year around 12 of August.
Although, this 2021 will be an “excellent” year to observe the Perseids, as it will happen a few days after the new moon on August 8, according to the National Astronomical Observatory (OAN).
This meteor shower is visible from across the Northern Hemisphere in midsummer. The speeds of these meteors can exceed 50 km / s and their activity rate can reach 200 meteors per hour. Although its peak time occurs on the nights of August 11-13, the Perseids usually begin to be seen around July 17 and end around August 24.
According to the OAN, its high activity, together with the favorable atmospheric conditions for observation during the boreal summer, makes 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.
The friction with atmospheric gases calcine and vaporize meteors They appear bright for a fraction of a second, forming what is popularly called 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. Meteoroids with a mass of less than one kilogram completely calcine in the atmosphere, but the largest and most dense (rocky or metallic in consistency) form meteorites: calcined remains that fall on the ground.
Every year in early August, the Earth 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 of 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 Perseus, hence their name.
The observation site can be any as long as it provides a dark sky. It is preferable to observe from a location with few obstacles to your vision (such as buildings, trees, or mountains), and do not use optical instruments that limit the field of vision.
Although the Perseids appear to come from the constellation Perseus, they can be seen anywhere in the sky. It is convenient to look towards the darkest areas, in the opposite direction to the position of the Moon if the observation is made before its sunset. The most comfortable thing is to lie down and wait for the view to get used to the dark.
The number of observable meteors per hour is highly variable. In a very dark place and with the radiant high above the horizon it can exceed a hundred. However, the number of meteors observed per hour can vary very quickly depending on the density of fragments in the comet’s wake, so specific predictions on specific numbers of meteors depending on the day and time are difficult to make and are often affected. of a high uncertainty.