The annual Perseid meteor shower has been underway since last month and is predicted to peak early next week on August 12 between 13:00 and 16:00 UT. The Perseids are the most popular meteor shower of the year and one of the highlights of the observing calendar, and many astronomical societies and interested individuals have made plans to travel to observe this special spectacle from a dark sky site.
The Perseids are active from 17 July to 24 August, and UK Meteorological Network cameras have already recorded activity. In particular, a dazzling Perseid fireball, estimated to be magnitude -4.4, was recently captured on the night of 1/2 August at 01:19 UT (see image).
This year, the peak means that the best chance of seeing the most meteors will be on the night of 12/13 August (Monday night to Tuesday morning), although observed meteor rates should still be good on the night before, on 11/12 August (Sunday night to Monday morning) and on 13/14 August. The Moon, which all too often seems a blight on chances of spotting the fainter Perseids, is not a major factor this year. It is in its waxing gibbous phase and sets at 11pm BST on 12 August. This leaves the field clear for pre-dawn meteor watching, as the radiant climbs ever higher in the east.
Meteor showers have a peak called the “zenith hourly rate” (ZHR). For the Perseids, the value is typically around 100 (sometimes between 100 and 150), although this hourly rate would only be observed if the shower's radiant was high up at the zenith and viewing conditions were perfect. In the real-world viewing world, from a reasonably good viewing site when the radiant is high up, it's not unreasonable for hourly rates to average around 40 meteors. Assuming clear, haze-free skies at a dark-sky site, observers can expect to see 50 to 70 meteors per hour near the peak.
The Perseid radiant is located at the northern edge of Perseus (see the graphic showing where it is), low in the northeastern sky as night falls, but rising to a considerable altitude of 50 degrees by about 2am BST. By that time, the areas of the sky where the Perseids are most likely to appear will be much better located than before midnight.
When you're observing meteors, don't stare at the point in the sky where the radiant is located. Perseid meteor trails will appear short and therefore be harder to see. You'll see many more shooting stars if you look at an area of the sky 30-40 degrees from the radiant (from where the meteor streaks may appear longer) and about 50 degrees above the horizon.
The Perseids are the result of debris from the periodic comet 109P/Swift–Tuttle, which breaks off along its 133-year orbit. They are fast, entering Earth's upper atmosphere at 60 km/s. The shower is known for producing large numbers of bright meteors and fireballs that often leave behind persistent trails or contrails.
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