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The Perseid Meteor Shower is Here!

Perseid Meteor Shower
Perseid Meteor Shower

Article by: W. Jerrold Samford, Environmental Compliance Specialist, Troutman Sanders

Earth has entered the debris stream of Comet Swift-Tuttle and this is causing the annual Perseid Meteor Shower. At their peak, the perseids commonly produce 50 to 75 meteors an hour - about 1 meteor per minute. The best time to watch will be the early mornings of August 12 - 13. Swift-Tuttle's debris field is very broad, so there are Perseid meteors in the sky now, and will be for days after the peak. The crescent moon in the sky is an accompanying joy, but will not cast enough light to mar the experience. Just go outside after midnight, look up toward the eastern sky and enjoy this spectacular sight. Learn more with NASA's What's Up: August 2021 Skywatching Tips video.

If you were able to trace the trajectories of all the Perseid meteors back to their “origin” in the sky (the radiant point), they would appear to originate in the constellation Perseus. To find Perseus, look to the northeast sky. Cassiopeia, looking like a “W” is familiar to many, and Perseus is just below. You do NOT need to find the radiant, or Perseus, to see the meteors.

perseids
Image: EarthSky.org

As the Earth rotates, the side facing the direction of its orbit around the Sun tends to scoop up more space debris. This part of the sky is directly overhead at dawn. For this reason the Perseids and other meteor showers are usually best viewed in the predawn hours. But remember – I am not responsible for the weather!

The Perseid meteor shower is caused by debris from Comet Swift-Tuttle. Every 133 years the huge comet swings through the inner solar system and leaves behind a trail of dust and gravel. When Earth passes through the debris, specks of comet-stuff hit the atmosphere at about 135,000 mph. At that speed, the bit of dust heats to over 3,000° F and even a tiny particle of dust makes a vivid streak of light--a meteor--when it disintegrates. This meteor shower is called the “Perseids” because it appears to originate in the portion of the sky inhabited by the constellation Perseus.

The Perseid meteor shower never fails to provide an impressive display and, due to its summertime appearance, it tends to provide the majority of meteors seen by non-astronomy enthusiasts. The records of Perseid activity date to the First Century. In Chinese annals, there are observations that in 36 AD "more than 100 meteors flew thither in the morning." Numerous references appear in Chinese, Japanese and Korean records throughout the 8th, 9th, 10th and 11th centuries, but only sporadic references are found between the 12th and 19th centuries. The Perseids have been referred to as the "tears of St. Lawrence", since meteors seemed to be in abundance during the festival of that saint on August 10th, but credit for the discovery of the shower's annual appearance is given to Quételet (Brussels), who, in 1835, reported that there was a shower occurring in August that emanated from the constellation Perseus.

The first observer to provide an hourly count for this shower was Eduard Heis (Münster), who found a maximum rate of 160 meteors per hour in 1839. Later observations by Heis and other observers around the world counted maximum rates typically falling between 37 and 88 per hour through 1858. The observed rates varied between 78 and 102 in 1861, according to estimates by four different observers, and, in 1863, three observers reported rates of 109 to 215 per hour. Although rates were still somewhat high in 1864, generally "normal" rates persisted throughout the remainder of the 19th-century.

In the late 1800's Giovanni Virginio Schiaparelli established the relationship between the Perseids and comet Swift-Tuttle. This was the first time a meteor shower had been positively identified with a comet. Although the comet is currently nowhere near Earth, debris left from the comet's wide tail intersects Earth's orbit.

Comet Swift-Tuttle’s next appearance in the area of our galaxy will be in the year 2126. I look forward to seeing it!

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