10:00 AM | *The "Great American" solar eclipse is not the only space event of interest in August...Perseid meteor shower peaks on August 12th*

On July 31st, 2017 James W. Young photographed a green Perseid fireball skimming the coast off Cannon Beach in western Oregon. "The Needles (rock outcroppings) to the right are just south of Haystack Rock," says Young. "The fireball was a pleasant surprise!"(photo courtesy spaceweather.com)

Overview
The “Great American” solar eclipse that is coming on August 21st is not the only space event of interest during the month of August.  The annual Perseid meteor shower has actually already begun and it will peak on Saturday, August 12th. The Perseid meteor shower comes every August as the Earth passes through a cloud of dust that comes from Comet Swift-Tuttle as it approaches the sun.  

Discussion
Earth's gravity pulls in some of the chunks of debris from Comet Swift-Tuttle — small rocks comprised of iron-nickel, stone, other minerals or a combination of these — which turn into bright balls of hot gas when entering Earth's atmosphere.  As darkness falls, the meteors appear to come from the constellation Perseus, hence the name; although late in the evening, the meteors originate higher in the sky than the constellation.  Perseid meteoroids hit our atmosphere at ~132,000 mph to produce the annual light show and this particular meteor shower is usually rich in “fireballs” because of the size of the parent comet.  Comet Swift-Tuttle has a huge nucleus – about 26 kilometers in diameter whereas most other comets are much smaller with nuclei only a few kilometers across.  As a result, Comet Swift-Tuttle produces a large number of meteoroids, many of which are large enough to produce fireballs.  In fact, the Perseid meteor shower is considered the “fireball champion” of all of the annual meteor showers.

The 2017 Perseid meteor shower will peak around 1 p.m. EDT (1700 GMT) on Aug. 12, so the nights of Aug. 11-12 and Aug. 12-13 should see the highest rates. The meteors appear to radiate out of the constellation Perseus, from which they take their name. Credit: NASA/JPL-Caltech
 

Since this year’s peak occurs in the middle of the day (~1pm) on Saturday the 12th, the night before and the night after this peak time will be relatively equal in terms of best viewing time periods.  Specifically, the best time to look this year will be during the nights of August 11th to 12th and 12th to 13th (i.e., Friday/Saturday and Saturday/Sunday).  The Perseids will be a little more difficult to see this year due to the presence of the bright gibbous moon which will be three-quarters full and will rise shortly before the shower hits its peak around midnight local time.  Rates are likely to be about half of what they normally would be because of the bright moonlight.  Instead of the normal 80 to 100 per hour, this year may feature 40 to 50 per hour in dark areas.  Typically, the meteors are only the size of pebbles, some as small as a grain of sand.  

Meteorologist Paul Dorian
Vencore, Inc.
vencoreweather.com