After the spectacular opening fireworks of the Chinese Olympics comes one of nature’s own finest displays – the Perseid meteor shower. In fact Earth began entering the dust stream that produces these shooting stars in July. But they will build to a peak in mid August when a single observer might see one or more a minute.
They are one of the year’s most reliable showers and a favourite for northern stargazers who can sit out and count them on warm summer nights.
The meteors are expected to build to a rate of 80-100 an hour at maximum on 12 August – that is the number one might be expected to see with the unaided eye under ideal sky conditions if the radiant were directly overhead.
The radiant is the point in the sky from which the meteors appear to diverge – an effect of perspective much like the way parallel lines of a rail track appear to converge into the distance.
It lies in the constellation of Perseus which gives the meteor shower its name, but the meteors themselves can be seen in any part of the sky. The radiant is low in the sky when darkness falls but climbs steadily through the night and highest rates are likely to be seen in the early hours.
Although the 12th is the night of maximum, it is worth watching on nights around that date too when rates are expected still to be very respectable. The waxing gibbous moon is low in the sky from mid-northern latitudes, setting around midnight. Conditions could therefore be ideal in the pre-dawn hours.
The Society for Popular Astronomy meteor section reports that a Finnish meteor expert, Esko Lyytinen, believes that the Earth may encounter a denser meteoroid trail for perhaps an hour or so centred on 05h26m UT on 12 August. He suggests this could give another peak of 100-300, or even higher. The timing could particularly favour US sky-watchers.
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