Perseid Meteor Shower Highlights the Dog Days’ Skies

August 12, 2015 clifftop CliffNotes

On a clear, dark night, with plenty of patience, but no optical aides, the average person might count about 3,000 viewable stars. A good pair of binoculars would add to the number; a good telescope would bring many more stars into sight; an observatory view would expand stargazing by orders of magnitude; and, the earth-orbiting Hubble telescope allows us to peer deeply into space.

Each view also is a look back in time as the immense distances mean starlight takes time to reach us. That drop of sunlight shinning on you? It traveled just over eight minutes from the sun to reach you. A naked-eye view of starlight means you’re looking at light from millennia past, but the views made possible by the Hubble telescope allow us to clearly see light billions of years old that began traveling shortly after the earliest origins of the cosmos.

Because stargazing provided foundational material for some of the earliest stories people told about their worldview and cultures, astronomy also offers glimpses of human history. We still refer to August as the “dog days” of summer and sometimes call the August moon the “dog moon.” As apt as the thought of dogs panting through the hottest days of the year, “dog days” as the name for August actually derives from the star observations of antiquity and the rising of Sirius — the Dog Star — in heliacal aspect, at the same time as the Sun. At the very end of July 2015, we had a “blue moon,” not at all a reference to blue shading, but to the European phrasing for a calendar month with two full moons, an event so rare – the next July with two full moons won’t occur for 19 years – that it’s a “once in a blue moon” timeframe.

The dog days of August also give us spectacular nighttime viewing as this is the month of the Perseid meteor shower, one of the best and most dependent meteor showers visible in North America. In Greek mythology, the Perseids refer to the children of Perseus and Andromeda. Perseus, son of the mortal woman Danae and the god Zeus, beheaded the snake-headed monster Gorgon Medusa, whose visage was so terrifying that beholders were turned to stone. He saved Andromeda from a sea monster and together they had seven sons and two daughters. Their most famous descendent was their great-grandson, the famous hero Heracles, also a son of Zeus. Meteors visible from earth appear to originate in the constellation Perseus and, so, are named for the children of the early Greek hero and his consort.

The actual origin of the meteors is a debris cloud stretched out and scattered in the orbit of comet Swift-Tuttle. Named for its 1862 discoverers, the comet has a 133-year orbit; historical records indicate observations by Chinese astronomers in 69 BC and in 188 AD. Numbers of visible meteors vary from year to year during Perseid activity, which generally ranges between late July to the last week of August, with the showers at peak between August 12 to 14. Moon phase and weather conditions greatly influence the number of meteors that may be seen.

The shower of meteors is best viewed by finding a location with minimal light pollution – that is, far from city lights – and looking towards the northeast sky. And, as a meteor shower is best viewed by naked eye watching, it’s also a good opportunity to get familiar with other features of the night sky, beginning with the constellations in the same neighborhood as Perseus: Andromeda and Triangulum to the west, Cassiopeia and Camelopardalis to the north, Ares and Taurus to the south, and Auriga to the east.

Excepting Camelopardus, all of these constellations were among the 48 listed by Ptolemy, a mathematician, astronomer and geographer, in the 2^nd Century; today the International Astronomical Union lists a total of 88 constellations. The search for patterns in the night sky – an insistence on perceiving, naming shapes, and creating narrative from the essential randomness of the visible stars – was by no means confined to the western traditions handed down to us by Ptolemy. Within the same area of sky as Perseus, early Chinese astronomers recognized four constellations.  Polynesian peoples, among the world’s best star-following navigators, perceived a constellation they interpreted as a great porpoise, encompassing sectors of Cassiopeia, Andromeda, Triangulum and Aries.

The modern convention of 88 named constellations was adopted in the 1930s. Under this scheme, the entire sky is covered and each constellation has precise boundaries. Constellations, still carrying the names of animals, human or mythological characters, or, even, objects, are maps of the sky, helping stargazers find their path through the night sky.

Clifftop is hosting a program devoted to stargazing, constellation finding, and the Perseid meteor shower. Our field trip will be held from 8 to 11 pm on Saturday August 15^th at the Paul Wightman Subterranean Nature Preserve. With good weather and unobstructed views we could enjoy as many as 60 to 100 meteors an hour during the evening’s Perseid meteor shower. Our host is amateur astronomer Tom Sudholt, Program Manager and Host at Radio Arts Foundation (RAF) St. Louis. Tom, a stargazer since childhood, will bring his 8-inch telescope allowing us to get some deep space views, looks at nebulae, and other wonders of the star-filled sky. We also will have discussions about naked eye astronomy, and the perspectives viewing the cosmos can bring. Attendees should wear weather appropriate clothing, sturdy boots or shoes (we’ll have a short, easy walk through grass and mowed areas), and bring a lawn chair, a small flashlight, and drinking water for themselves (mosquito repellant also is a good idea). This is a weather dependant event (subject to cancelation should we have rain or even very heavy cloud cover), so participants must register by email to Clifftop@htc.net or by ‘phone, 618-458-4674; registration must be made by 12 August.

CLIFFTOP, a local nonprofit organization, is focused on preserving and protecting area bluff lands.

A version of this article appeared in the 7 August 2015 edition of the Monroe County Independent.

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