Saint Lawrence (or Lawrence of Huesca), martyr and one of the first seven Deacons (guardians of the treasure) of the Catholic Church, perished on a burning grill, under the order of the Roman Emperor, on August 10, 258 (AD), in the eternal city.
I don't know whether this date is according to the Julian or Gregorian calendar, but I lean more towards the latter. Not because this is the calendar we follow here in the West, but because the 10th of August, when the Catholic liturgical feast is celebrated in honor of the Christian martyr, is among the days when it is possible to observe a greater intensity and number of shooting stars crossing the zenith on warm summer nights.
The popular tradition named the shower of stars, which dazzles the starry vault these days, as “the tears of São Lourenço”. The overlap between the date of his death and the astronomical event makes me place the beginning of popular attribution after 1582, the year in which Pope Gregory XIII promulgated the calendar with his name.
In other words, it was only in the summer of 1583 that our planet Earth, in its inexorable translation around the Sun, sublimated a swarm of meteors called the Perseid Cloud between the 8th and 14th of August in the Gregorian calendar.
Just out of curiosity, let's say that the 10th of August, in our calendar, would be the 28th of July in the Julian calendar. And the 13th of August, when a peak in the “precipitation” of shooting stars known as Perseids is normally predicted, would correspond to the 31st of July, according to Julius Caesar.
But let us look a little at the starry sky and let ourselves be bathed in cosmic dust. A shooting star, despite its name, is not a star that suddenly accelerates, leaving a trail behind for our wonder.
It is actually a meteoroid that entered the Earth's atmosphere and that, due to friction, caused a meteor to sublimate a desire of a persistent observer.
Every year, on the night of the 12th to the 13th of August, we don't need to look far to impress the retina from meteoric movement as we look at the celestial vault.
This is because planet Earth crosses, at this time of year, a region of interplanetary space dotted with meteoroids, little larger than a pea, and which sprinkle the path taken by the tail of the giant periodic comet Swift-Tuttle (about 28 km in diameter !) in its orbit around the Sun, which takes 133 Earth years!
The first observation record of the passage of the comet is of Chinese origin and dates from 69 BC The last occurred in 1992, the date of its rediscovery.
As with any other comet, when it approaches the Sun, the Dantesque increase in temperature causes small fragments of the comet's nucleus to break off and trace the trajectory of its orbit in space.
In August, our planet crosses the meteoritic trail of Swift-Tuttle's orbit, and an observer in the northern hemisphere will have the sensation of contemplating a shower of meteoroids, which seem to gush from a single source (the radiant one) in the nearby celestial sphere of the constellation Perseus.
It is common to see a hundred meteors volatilize in the space of an hour, crossing the vault at an average entry speed of about 200 km/h (data from the Astronomical Observatory of Lisbon).
The maximum activity this year takes place on the 13th of August between 03:00 and 16:00. In Portugal, the best time to observe it with the naked eye will be around 03:00, where you can observe up to 110 meteors per hour.
Author: António Piedade
Science in the Regional Press – Ciência Viva
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