The Perseid meteor shower, the most reliably active meteor shower of the year, peaks on the night of August 11-12, 2015. The Perseids are a favorite of many stargazers. They happen in the northern summer, which makes for comfortable viewing. They display more bright meteors than most showers, usually about 50-60 per hour. And this year, the nearly-new Moon will not get in this way of the Perseids, so 2015 will be an excellent year to see this meteor shower.
Like most meteor showers, the Perseids are simply dust-sized pieces of icy debris expelled from a comet, in this case, Comet Swift-Tuttle. As the Earth passes through the comet’s debris trail once each year, some particles streak through our atmosphere and heat up, leaving a transient bright glow we call a meteor. The tiny particles burn up in the atmosphere. Very few, if any, make it to the Earth’s surface. Some hit the moon, too, though they’re too faint to see, even with a telescope.
While the meteors move into the Earth’s atmosphere on parallel paths, they appear to radiate from a single point in the sky called a radiant. The effect is similar to falling snowflakes that seem to radiate from a point in front of your windshield as you drive into a snowstorm. The radiant of the Perseid meteors is found in the northern constellation Perseus close to the neighboring constellation Cassoipeia.
The Perseids build slowly, starting in late July when you might see 3 to 4 an hour. They peak when Earth passes through the thickest part of the debris stream on August 11-12. At the peak of the show, in clear, dark sky, you might see as many as 60 meteors an hour.
For the best view of the Perseids, look for meteors late on August 11 and the early morning of August 12. After midnight is best… that’s when the Earth turns into the stream of particles from Swift-Tuttle. Avoid ambient light if you can. Lie on a reclining chair or a blanket on the ground, and simply look up. You don’t need binoculars or a telescope. Nor do you need to look right at Perseus: the meteors can appear anywhere in the sky. Those with long streaks come into the atmosphere at an oblique angle. Those with shorter streaks enter the atmosphere at a steep angle and come more directly towards you… and no, they will not hit you! Because the radiant lies in Perseus, northern-hemisphere observers get the best view, although southerners will see some, too.
In medieval Europe, the Perseids were called the “Tears of St. Lawrence” because they occur near the anniversary of the death of Laurentius, a Christian deacon who was martyred by the Roman Emperor Valerian in the year 258 A.D. The first recorded observation of the Perseids was by Chinese astronomers in 36 A.D.
(Image at top courtesy of David Kingham)
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