John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
The best shower of the year is known for its intense, colorful "fireballs."
City dwellers have so much fun drained out of astronomical spectacles, with light pollution covering the celestial dome like gauze. But tonight's long-awaited Perseid shower might be different, as the annual bombardment is known for its super-charged meteors that paint even hazy urban skies with plasma streaks.
The impressive visual artillery of the Perseids relates to their source, Comet Swift-Tuttle, whose orbit is close enough to the earth that dust from its tail gets pulled into the atmosphere. The space detritus is thick and spiked with relatively large pieces, so that when it whizzes down at 132,000 mph it creates fireballs—intense, colorful meteors that can leave lingering trails of smoke and ionized air. During some years, watchers in darker rural areas can expect to see several of these ramped-up meteors and a flurry of smaller ones, adding up to 100 or more sightings each hour.
This year isn't the best for catching the Perseids at their prime, as an almost-full moon will be lighting the heavens. Astronomers are predicting peak rates of 30 to 40 visible meteors per hour, and in brighter city environments you can expect to see one-tenth that number. But if you were to pick one meteor shower that's worth being all crusty-eyed for the next day, it's the Perseids. Science has proven it: A NASA study recently deemed it the "best" meteor shower due to its stunning volley of fireballs. (Suck it, Geminids!)
Start looking upward around 10:30 p.m., local time. Rates should increase through the night and peak around 3 to 4 a.m. If the weather cooperates, the shower should be visible over a huge part of the planet, as shown in this NASA map:
To break those zones down into numbers, "best visibility" equates to 30 to 40 an hour in a dark environment, "low rates" is less than 10 an hour, and "very low rates" is less than five an hour. To increase your chances of spotting these flaming fliers, check out our guide to watching meteors in the big city. And if you want to hang with the big boys during the show, NASA will be holding a live-chat tonight beginning at 11 p.m. EDT.