Shooting stars and starry skies: the Perseids are coming

August 05, 2023

Every year mid-August, a noticably large number of shooting stars can be seen in the night sky. Around 12 August, the Earth crosses a swarm of cosmic dust particles which become visible when they enter Earth's atmosphere. Under optimal conditions, meteors can be seen darting across the sky every one to two minutes. This year, the premises are particularly favorable for this celestial spectacle, because the maximum of the Perseids is on a weekend and the Moon does not brighten the sky.

The Perseids are certainly the most famous of all meteor showers because during the warm summer nights in August many people are still outside at late hours anyway and can easily observe the shooting stars "along the way". In addition, the Perseids are very reliable: They return every year with approximately the same numbers of shooting stars and are visible in a time period of several weeks. To see the Geminids in mid-December and the Quadrantids in early January, which have similar meteor rates, observers have to go out during the cold winter nights, which are more often affected by bad weather than in summer.

Most Perseids are visible after midnight, when the Earth dips heads-on into the stream. Their theoretical peak will be reached in the morning of 13 August. In the nights from 12 to 13 August (Saturday to Sunday), as well as from the 13 to 14 August (Sunday to Monday) numerous shooting stars can be expected. Individual observers can see up to 30 to 50 meteors per hour. It is best to look to the east, where the constellation Perseus can be found, after which the Perseids were named because they seem to come from this constellation. Every meteor shower has such a "radiant" or point of emission.

On its orbit around the Sun, the Earth crosses the paths of asteroids and comets that have left particles behind along their orbit, which in turn become visible as shooting stars when they burn up in Earth's atmosphere. In reality you don't see the particles themselves, but the air around them, which is heated up by friction and starts to glow when the particles are slowed down as they fall through Earth's atmosphere.

In case of the Perseids, the culprit is comet 109P/Swift-Tuttle, which was discovered independently by Lewis Swift and Horace Tuttle on 19 July 1862. It takes this comet about 133 years to complete its orbit around the Sun. In 1992 it could be observed again, and its next visibility is expected only for the year 2126.

The constellation Perseus is a classic autumn and winter constellation. In the middle of August, Perseus and with it the radiant of the Perseids rises in the evening sky and then climbs higher and higher in the sky during the night. Therefore most shooting stars are seen in the late evening and - even better - in the early morning hours, when our viewing direction is along the direction of the "snow storm" of shooting stars.

The Moon will be a few days before new Moon, and rises on Sunday morning only around 2 CEST in the northeast (on Monday morning shortly before 3 CEST) and shows up as a thin crescent. To the right of Perseus, the bright planet Jupiter is visible as well.

The occurrence of the Perseids is not limited to the short time of the maximum, you can try your luck also in the days before and after - ideally comfortably on a garden chair with a relaxed view upwards. However, light pollution by artificial light sources impairs the visibility of the fainter shooting stars. The ideal observing location is therefore far away from the cities and has a free view of the horizion, for example on a hill. So if you are limited to the view from your living room window in a big city, you should be patient and expect fewer shooting stars.

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