Categories: Sky Reports
Perseid meteors. Credit Rafael Schmall/Universities Space Research Association.
Choosing the topic for this week’s Sky Report is simple – the annual Perseid Meteor Shower which peaks on the night of Saturday the 12th and the morning of the 13th – a weekend even!
Meteors are bits of dust or rock that came from elsewhere in the solar system and that collide with the earth. Perseid meteors fall through our atmosphere so fast, at 37 miles/second, that the air abruptly heats them to 3,000°. The outer surface ablates, or is swept away, as soon as it gets that hot, sometimes leaving a glowing trail that lasts several seconds or more. Then the next layer is instantly heated and ablates away until nothing is left. A bright meteor is caused by something the size of a pea, and you see it because it’s dazzlingly bright against a dark background. Meteors typically are consumed while still more than 50 miles high.
Perseid meteors come from a comet named Swift-Tuttle for its discoverers. Comets are “dirty snowballs” – mixtures of dust and ice – that orbit the sun on elliptical paths that take them far from and then close to the sun. When close, the sun heats the ice which evaporates (sublimes, actually, in a vacuum), releasing the dust. That dust follows in the orbit of the comet. Gradually the dust disburses into a cloud, which then stretches into a river, millions of miles wide along the comet’s entire orbit. When the earth passes through that river, we see a swarm of meteors that can last one night or weeks.
The Perseid Meteors (which radiate from the direction of the constellation Perseus, and hence their name) began in mid-July when the earth entered the outer edge of that river and they continue through August, but the night of August 12th is when we are in the deepest part and see the most meteors.
To see them, find a comfortable spot where it’s dark with a wide view of the sky (perhaps a lounge chair in a clearing) and look up. You’ll see a few as darkness falls, but you’ll see many more as the hours pass; the later the better and the best time is early morning. They’ll radiate from the direction of Perseus in the northeast, but they’ll appear all over the sky. Note that the ones nearest Perseus leave short, slow trails –- because they’re coming nearly straight at us – while meteors farther from the radiant point are traveling laterally and leave swifter, longer streaks.
If you’re in a dark location expect to see up to 60 meteors per hour in the early morning. The waning crescent moon won’t interfere – a huge bonus.
One-third as many meteors fall the night before and after, so it’s not a one-night event.
While watching meteors notice bright Jupiter, which rises around midnight, and fainter Saturn, which is halfway up the southern sky around 2 a.m. Mars is very low in the west in evening twilight. And Venus passes closest to the sun on the 12th.
Stellar Vista Observatory provides portable telescopes and tripod mounted binocular kits on loan for free to residents and visitors in Kane County. Enhance your enjoyment of the night sky! To learn more, request a loan, or attend one of SVO’s free public star parties for 2023, visit https://stellarvistaobservatory.org/ or drop in to the Kane County Office of Tourism.