Perseids: summer nights and the Tears of St Lawrence

The shower that suits holidays

Part of the Perseids' fame is simple convenience. The peak falls in the northern summer, when nights are warm, schools are out and the Milky Way is high. You can stay up late in a T-shirt, which is more than you can say for the January showers.

It is also a prolific shower, with many bright meteors and frequent fireballs that leave persistent trains. Because Perseus sits low in the northeast at nightfall, the first hours are quieter but often bring a few long, graceful earthgrazers, and the show builds as the radiant climbs.

Tears of St Lawrence

Medieval Europeans noticed that the meteors arrive around 10 August, the feast day of St Lawrence, a Roman deacon martyred in the third century. The streaks became known as his fiery tears. The name is a pleasant piece of folklore and tells us the shower has been noticed for at least a thousand years.

The modern explanation came in 1866, when Giovanni Schiaparelli connected the shower with Comet Swift–Tuttle.

The comet behind it

Swift–Tuttle is a huge comet, with a nucleus about 26 km across, more than twice the size of the one thought to have ended the dinosaurs. It orbits the Sun every 133 years, shedding dust that now forms a long band. Perseid grains hit the atmosphere at about 59 km per second.

Planning your night

• Start after about 10 pm. The radiant, in Perseus, rises in the northeast and is high only after midnight.
• Look anywhere high. You do not need to find Perseus, just lie back and take in a wide stretch of sky.
• Count the nights either side. The shower is broad, so the nights before and after the peak are also good.
• Bring company. Everyone sees a different set of meteors, and shouting out "there!" is half the fun.

Beyond the northern hemisphere

People in the south see fewer, because the radiant stays low. Still, it is worth a try from the tropics. Compare this shower with the Geminids, its winter rival, or browse the meteor showers hub.