The Perseids, the most widely observed and dependable of the annual meteor displays, will peak during the overnight hours of Thursday, Aug. 11 into the morning of Friday, Aug. 12, and this year has all the earmarks of being a spectacular show.
First, there is the situation regarding the moon. At first glance, it appears that the viewing conditions aren’t very good, as the peak night coincides with a waxing gibbous moon, 63-percent illuminated. Its bright light no doubt will wash out all but the very brightest of these swift streaks, which chiefly will emanate from out of the northeast part of the sky. However, there is some very good news: Early Friday morning (Aug. 12), the moon will set near 1:00 a.m. local time. Dawn breaks at about 4:20 a.m. around the mid-northern latitudes. Between those two times, there will be a nearly 3.5-hour “window” during which the sky will be totally dark.
Another reason the Perseids could put on a better-than-average show this year is a gravitational assist from Jupiter.
Most meteor showers evolve from comets. The cometary parent of the Perseids is a comet known as Swift-Tuttle. This comet takes approximately 130 years to make one trip around the sun. It was discovered in 1862 and last appeared in our skies in 1992. (It’s due back in 2126.) Comets are composed chiefly of frozen gases, and meteoroids that are mixed in with that gas — the bits and pieces that have flaked off from the comet’s solid center or nucleus.
Like all comets, Swift-Tuttle leaves behind streams of tiny particles ranging in size from large grains of sand to small pebbles, but with the consistency of cigar ash. They’re invisible to people on Earth until, upon entering our atmosphere with immense velocity — 37 miles per second (60 kilometers per second) — they blaze up within the span of a heartbeat and streak across the sky in a brief, blazing finale. Comet Swift-Tuttle probably has passed the sun hundreds of times to produce the present stream of Perseid meteors.
The meteoroids have become distributed all around the comet’s elongated elliptical orbit, which takes them out beyond the realms of Pluto and ultimately brings them back to intersect Earth’s orbit at almost a right angle, producing a fairly predictable meteor display that lasts for several days in mid-August.
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SOURCE: Space.com, Joe Rao