Tonight's forecasted clear skies could permit us a glimpse of one of the night sky's more camera-shy annual attractions: the Boötids meteor shower.
The Boötids are so named because they appear to emanate from near the constellation Boötes, the herdsman. Most years, they are a pretty low-key affair, with only a few visible meteors per hour.
Every now and then, though, they can really knock your socks off. That's what happened in both 1998 and 2004, when the Boötids erupted at a rate of 50-100 visible meteors per hour. Prior to that, they hadn't flared up since the 1920s. Astronomers still don't know precisely why the rate of the Boötids varies so wildly.
Like the other annual meteor showers, the Boötids are a result of the Earth's orbit intersecting with the debris trail left behind by an orbiting comet. In this case, the comet is the inelegantly named 7P/Pons–Winnecke, a three-mile wide hunk of ice and dust that goes around the Sun about once every 6 1/4 years. When those tiny flecks of debris hit the Earth's upper atmosphere, they are consumed in a flash of heat. Sometimes, that flash is bright enough that we can see it from the ground,
In addition to their scarcity, another signature characteristic of the Boötids is that they typically enter the atmosphere more slowly than most meteors. When they appear, the most spectacular Boötids can linger in the sky for two or three seconds, unlike the blink-and-you'll-miss-it appearances of most "shooting stars."
Some astronomers expect this year's Boötids to be another snoozer, but the fact that the waxing half-moon will be fairly low in the western sky by midnight means that arriving meteors won't have to compete with quite so much moonlight to be visible to the naked eye.
To look for the Boötids, find the constellation Ursa Major—The Big Dipper—in the northern sky. Follow the Dipper's "handle" out to its end star, Alkaid (Arabic for "the leader"). If you continue following the handle's imaginary curve past Alkaid, you'll arrive at Arcturus in Boötes. Generally, the Boötids will show up in the area of the sky between these two stars (see the illustration above).
So spritz yourself with a bit of mosquito repellent, grab a loved one (and perhaps a cold one), and spend an hour under the stars before bed tonight. At worst, you'll get in some quality time outdoors on what ought to be a beautiful evening. And we might just get lucky.