Perseid Meteor Shower

Over the next week the Perseid meteor shower will peak. As the most reliable shower each year this is also the most viewed meteor shower. Plentiful shooting stars combined with warm summer evenings makes this shower the easiest and most comfortable to view across much of the northern hemisphere. Quite a difference from the other reliable showers such as the Leonids and Quadrantids, that occur in November and January. Consider a warm summer night under a dark sky full of stars, a picnic blanket, relaxing while shooting stars streak across the sky. What could be better?

Leonids in Orion
A pair of Leonid meteors streak through Orion

The Perseid meteor shower occurs when the Earth passes through a stream of debris along the orbit of Comet Swift-Tuttle. This shower has been consistent throughout recorded history, mentioned in Chinese, Japanese and Korean records as early as the 1st century. Active from July 17th to August 24th, the shower will build slowly for weeks before the peak. A week before or after peak the shower can still be seen with around 20 meteors each hour. The shower is a northern hemisphere event, for southern observers the radiant never rises above the horizon.

A typical Perseid shower will produce up to 60-100 meteors an hour, what regular meteor observers would call 60-100ZHR. This is what a typical observer would see given a dark sky and good conditions with the shower radiant at zenith, a metric called zenithal hourly rate or ZHR. You can estimate this rate by counting the meteors seen in a shorter period. If you count the meteors that you see for ten minutes and multiply by 6 you would have a reasonable estimate of ZHR. As the rate of meteor arrival is irregular it is necessary to count for ten minutes or more to achieve a decent average rate. Conditions such as light pollution or clouds will result in some faint meteors being missed and a lower count.

The 2019 Persieds are mostly spoiled by moonlight, full moon occurring on the 15th while the peak is predicted for the 13th from 02:00 to 15:00UT. It should be possible to observe a few in the last hours before dawn on the morning of the 13th when the Moon is low and before sunrise. As the Perseid peak is a long and broad good activity might be seen for a week or more either side of this peak. Thus the preceding mornings may also be good. After peak on the 13th the Moon moves into the morning sky along with the radiant.

First quarter Moon on August 7 allow the observers to record the ascend towards the maximum of the Perseids (007 PER) which is due between λ⊙ ≈ 139.8 to 140.3 , equivalent to 2019 August 13 02h to 15h UT. Table 5d of Peter Jenniskens (2006) lists the encounter of a filament on August 13 at 02h UT just at the beginning of the above mentioned interval with a possible ZHR of about 110.

IMO 2019 Meteor Calendar

Watching meteors requires no more equipment than your eyes and a dark sky, and can be enjoyable for just about anyone. A good meteor shower is a great excuse to get out under a dark sky and enjoy the stars. Conditions should be quite good, why not make a point to watch the Perseids this year?

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on Mauna Kea, Hawai'i.

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