This is an excellent year to observe the Perseids because, during the maximum, the Moon will be in the new moon phase and will not be an impediment. The best time to observe them is the early morning of Saturday 12 to Sunday 13 August, but since the end of July they have been able to see some. We just need a place protected from artificial light, a clear sky of clouds and a little patience.

HOW TO OBSERVE THE PERSEIDS

This month of August will be very favorable for the observation of the Perseids because its maximum happens very close to the novilunio (which will take place on the 16th). Therefore, contrary to what happened last year, this time the light of the Moon will not be an impediment to see the shooting stars.

The Radiant of the PerseidsOAN (IGN)

The number of observable Perseids per hour is highly variable. In a very dark place and with the radiant high above the horizon can exceed a hundred. However, the number of meteors observed per hour can vary very rapidly as the density of rocky fragments varies in the area of space traversed by the Earth, so concrete predictions about the specific number of meteors depending on the day and time are difficult to make and are usually affected by high uncertainty.

WHEN IS THE BEST TIME TO SEE THE METEOR SHOWER

The highest activity of the Perseids (measured in number of meteors per hour) will be reached in the early hours of Saturday, August 12 to Sunday, August 13. The best times to see more and brighter meteors are from dusk until 3am or 4am. It is when the edge of the waning Moon has not yet risen and when the constellation of Perseus is already high above the horizon.

Although the radiant of this shower of stars is in the constellation of Perseus, it is not necessary to know the constellations, nor is it essential to look towards Perseus, to see the Perseids. Shooting stars can appear anywhere in the celestial vault, although they all seem to come from that point called radiant.

Perseids have been seen from July 23 to August 22, approximately, but it must be borne in mind that the full moon took place on August 1, so the last days of July and the first days of August were not especially favorable for observation. But, as the days have progressed, the activity of the Perseids has been growing. Until the 22nd, there will be the best conditions to observe a greater number of meteors.

FROM WHERE

The number of meteors observable per hour looking towards the zenith may exceed one hundred, under optimal conditions, that is, observing on nights of maximum activity, with the constellation of Perseus high above the horizon, without moon, without clouds and without light pollution. In other less than ideal conditions, the location of the observer is what determines, to a large extent, the number of meteors observed: it is always preferable to monitor the clearest area of clouds and the most free of light pollution.

The fact is that, every day that passes, it is more and more difficult to find very dark places and almost all peninsular observers will be located in areas with appreciable light pollution. It is therefore advisable to get as far as possible from the cities because their luminaires pollute the sky up to hundreds of kilometers away. Therefore, from a reasonably dark place on the Peninsula, we should not expect to see more than a couple dozen meteors per hour.

WHAT ARE SHOOTING STARS

First of all: shooting stars are not stars. They are particles or small fragments lost by comets. Indeed, as comets describe their orbits around the Sun, they throw 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 periodic comet, along its repeated turns around the Sun, thus forms a ring in which countless fragments are found. When the Earth, in its orbital motion, 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.

The Perseids occur when the Earth reaches the trail left by the Swift-TuttleSky&Telescope/RB

The height at which a meteor becomes bright depends on the speed of penetration into the atmosphere, but is usually around 100 kilometers. However, the high brightness and high transverse speed of some meteors cause a spectacular effect, causing the illusion in the observer that they are very close. Meteoroids of mass less than one kilogram are completely calcined in the atmosphere, but the largest and densest (of rocky or metallic consistency), form meteorites: calcined remains that fall on the ground.

ALSO INTERESTING

This shower of stars of the Perseids is created when, as every year at this time, the Earth, on its way around the Sun, crosses an area populated by the rocky fragments thrown by the periodic comet 109P / Swift-Tuttle when visiting this region every 133 years.

The Perseids were particularly active in 1992, when comet Swift-Tuttle passed close to the Sun. The comet's next approach to the Sun (perihelion) will be in the year 2126.

The Perseids are visible from all over the Northern Hemisphere in midsummer. The speeds of these meteors can exceed 50 kilometers per second (180,000 kilometers per hour). Their high activity, coupled with favorable atmospheric conditions for observation during the boreal summer, makes the Perseids the most easily observable and popular meteor shower.

In order of importance of their activity, on average, the Perseids constitute the third meteor shower of those that happen in the year. Both the Quadrantids (visible in January) and the Geminids (in December) usually generate more meteors per hour. Although they show a more irregular behavior, the Leonids (in mid-November) are usually as spectacular as the Perseids.

Due to the proximity of the maximum of this meteor shower to August 10, the feast day of the Spanish martyr who was burned on a grill in Rome in the year 258, the Perseids are also called 'Tears of San Lorenzo'.

Rafael Bachiller is director of the National Astronomical Observatory (Instituto Geográfico Nacional) and academician of the Royal Academy of Doctors of Spain.

  • Astronomy