macpuzl
By Chuck McPartlin
Coming to Santa Barbara’s late night and early morning skies on August 11/12 and 12/13 is the peak of one of the most reliable meteor showers each year – the Perseid meteor shower.
Every August, the Earth passes through the clouds of debris left behind by the periodic Comet Swift-Tuttle, and bits of space litter (meteoroids) moving at high speed enter our atmosphere, compressing and heating a column of air in front of them that fluoresces to produce the streaks of light that we call meteors. Most of these bits are no larger than a grain of sand, but their arrival at a cosmic velocity of 37 miles per second provides ample kinetic energy. Material ablated from the meteoroid as the hot air transfers heat to its outer layers may additionally fluoresce with a colorful tinge, depending on its composition. Atmospheric oxygen and nitrogen give a reddish hue. Sodium and iron glow orangey yellow, magnesium glows bluish green, and calcium glows violet.
Here’s a NASA image by Bill Ingalls of a bright Perseid during the 2016 shower, from a dark sky site in West Virginia. Perseus is in the center of the image, with Cassiopeia above and left. The meteor was moving from left to right.
Meteor showers can be rather disappointing for beginning skywatchers. They are often pitched by the media as awesome spectacles, pumping up the expectations of the public for a continuous stream of impressive fireballs. This type of show only rarely happens, largely because many meteors are dim, and light pollution obscures most of the dimmer meteors. Also, the best viewing hours are usually after midnight, when you’re facing into the direction the Earth is orbiting, and get more bugs on your windshield. The prospect of staying out late and feeding mosquitos to see one meteor per minute or so can be rather off-putting.
The Perseids actually cause increased meteor activity from July 17 to August 26. At their peak, from a dark site, you can expect to see a bit over one meteor per minute, with occasional bursts. The nice thing about the Perseids is that they are fast and bright, with a higher percentage of fireballs than most showers, so the ones you do see are more likely to be rewarding.
You can see the daily fireball plot at spaceweather.com to watch their activity ramp up and down.
To improve your chances of seeing the meteors that do occur, go to a dark location with a good view of the sky, and plop down with your feet to the northeast (toward Ojai from Santa Barbara). Meteors may show up in any part of the sky, but they will appear to be radiating from a spot in the constellation Perseus, just to the right and below the W form of Cassiopeia. Lie back or sit down, looking at as much sky overhead as you can. Veteran meteor watchers sit in sleeping bags on lounge chairs to stay comfortable. We’ll have good Moon phase conditions this year, so skies will be dark except for local light pollution.
Read the Sky & Telescope article linked below to find out about the discovery that the Perseids were an annual shower. As an appetizer, attend the monthly star party at the Santa Barbara Museum of Natural History on Saturday, August 11, and you may spot some early Perseids, along with views of Venus, Jupiter, Saturn, and Mars. We’ll have to close down at 10 PM because of neighborhood restrictions on museum activities, but you can head up into the mountains afterward and on Sunday night for the main course.
References for a Cloudy Evening
