Set your alarm clocks; one of the best meteor showers of the year is about to gear up this week! The Perseid meteors are one of the most dependable annual showers of the summer season, with a typical zenithal hourly rate (ZHR) of up towards 60-100 per hour. This year however, we could be in for a treat; there is evidence that we may intercept a fresh stream shed by progenitor comet Swift-Tuttle in 1610. We have never passed through this particular stream before; predictions are trending towards a brief ZHR of up towards 200! Don’t forget, however, that ZHR is optimal; this assumes the radiant is directly overhead and that there is no light pollution. The shower peaks morning of Wednesday August 12th, although it would be worth it to peek at the sky a few days prior to see what we might be in for. This year, the timing actually favors the North American continent! Now for the bad news; the waning gibbous Moon will be rising just before midnight in the constellation Aries, and be about 63% illuminated. If this is your chief source of light pollution, try to position yourself for observing in a way that blocks the Moon behind a hill, peak of a roof, whatever is handy. The Perseids are a true treat because they occur in the northern hemisphere summer, when its generally pleasant to lay outside. And school’s still out, to boot! Be sure not to miss this one; the only observing equipment you need is your eyes. If you can convince a friend to observe with you in the wee hours, you can collectively cover more sky. The radiant is located in the constellation Perseus (hence the name) which will be high in the north east. And don’t forget the bug spray!
The astro-term for this week is meteor stream. All meteors originate from a parent comet, or very rarely, an asteroid. Even the largest fireball you see in a given meteor shower is probably not larger than a pea, and most meteor streaks are caused by mere dust grains. These grains are dispersed along the orbit of the comet that shed them, and if that path intersects Earth’s, a shower occurs. Meteor streams evolve over time; some are pretty evenly distributed, while others like the Leonids tend to be clumpy. Only in the last decade or so has the modeling of meteor streams approached effective prediction of what we see in reality. And don’t forget, the front wind shield of the car gets the bug splatter, meaning that you’ll see many more meteors in the early AM!