As always, the meteor stream of the Perseids is one of the highlights of the night sky in the first half of August, the maximum is reached around August 12. This year, the night from Saturday to Sunday is especially suitable, the moon is only a thin crescent and rises late. But will the weather play along?
From the beginning to the middle of August it is worth to have a look at the sky, because on clear nights numerous shooting stars can be observed. They belong to the so-called Perseids. They are also called"Tears of Laurentius" because they appear around August 10, the name day of St. Laurentius of Rome.
What are the Perseids?
The Perseids are a meteor shower that peaks annually in August. Every year at this time, the Earth, as it orbits the Sun, is immersed in a cloud of debris left behind by Comet 109P/Swift-Tuttle as it travels through space. The dust particles hit the Earth's atmosphere at high speed (in this case 59 km/s) and evaporate already at an altitude of about 100 km by friction with the air molecules. These are ionized thereby. The shooting star is not the incandescent dust particle itself, but becomes visible by the recombination glow of the ionized air."Meteor" is the technical term for"shooting star." Not to be confused with"meteorite" – which is a celestial body that does not burn up completely when it enters the Earth's atmosphere and therefore reaches the ground.
The best chances to observe the nocturnal celestial lights are from August 9 to August 15. The highest probability is during the night of August 12-13. Between 10 p.m. and 4 a.m. potentially up to 100 passing shooting stars can be seen per hour. However, this value is purely theoretical and depends on many factors. Among other things, this is the height of the radiant in the sky, light pollution (moon, artificial light in densely populated areas) and of course cloud cover.
Shooting star showers seem to emanate from a specific point in the sky called the radiant. Although the meteors do not appear exactly at this point, if you extend their tracks in the sky, they cross in it. This has purely perspective reasons, because actually the shooting stars are parallel to each other. The constellation in which this apparent point of origin is located is the namesake of the respective meteor stream (the Geminids in Gemini, the Leonids in Leo, the May Aquarids in Aquarius.... In this case it lies in the area of the constellation Perseus, more exactly the head of it (so actually already almost between Perseus and Cassiopeia). The radiant rises higher as the night progresses, which is why the rate tends to increase. The peak is reached around 3 to 4 o'clock. Although the radian continues to rise after that and is almost at zenith in the morning, the sky becomes increasingly brighter again due to the approaching sunrise.
Fig. 1: Saturday, August 12 23:00 CEST. Radiant in the upper part of the constellation Perseus, moon still below the horizon; Source: timeanddate.de
The fall rate is irregular and purely random. There are longer phases without a single meteor, then again several in one minute. In any case, 20 to 40 shooting stars per hour are much more realistic than the theoretical 100. In general, after a maximum in 2018, the Perseids were somewhat weaker again, which is also to be expected for this year. The best observation points are far away from big cities and on hills and mountains (for a wide horizon). A little patience is required in any case, it is best to make yourself comfortable on a lounger or sleeping mat and watch the sky in a relaxed way.
And the weather?
Basically, it looks good in this respect, too! In the next few days, a high will dominate our weather. The nights are slightly cloudy to clear, now and then high cloud veils pass through. Also the temperatures will be much more pleasant for stargazers. Until Saturday it will be very warm to hot again, even after sunset the values will be above 20 degrees for a long time.
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