Star Points for March, 2002; by Curtis Roelle Sky Treats Closer to Home When talking about observing the night sky from a back yard there is typically the assumption that we are talking about objects that are distant in relation to our daily experiences. Stars dozens or hundreds of light years away, clusters of stars and nebulae thousands of light years away, and galaxies whose distances are measured by light years in the tens or hundreds of millions. Even when we discuss planets that are millions of miles away or the nearby Moon whose distance is a mere 250 thousand miles we are talking about objects beyond our world. Observable phenomena occurring much closer and within our own atmosphere is also visible to the unaided eye. In December I mentioned a brilliant Aurora Borealis that was visible across much of the country in November. Photographs from my back yard observatory are still available on the Star Points web site. Commonly referred to as "northern lights," the Aurora Borealis is seen in several forms and can be vividly colorful as demonstrated in the photographs mentioned above. The Auroral glow occurs as charged particles belched from the Sun rain down along the Earth's magnetic field onto the planet's magnetic poles. The particles strike the upper atmosphere which fluoresces, or glows. Sometimes these displays can become so intense that they become visible at more southerly Latitudes. Auroras are closely linked to astronomy because they are caused in part by the Sun. There are other phenomena which occur in our atmosphere that are not necessarily astronomical in origin. Some in fact may be viewed during daylight. The rainbow is a common example. Winter is an especially good time to spot other varieties of atmospheric phenomena. Even on a clear day ice crystals may be suspended in the sky. There are two main types of ice crystals and each is hexagonal (i.e. 6 sided). Plate crystals are flat and thin with six sides. Column crystals are tall with six sides and flat ends. Each crystal acts as a tiny hexagonal prism for reflecting or refracting light. Have you ever seen a "halo" around the Moon or Sun? The ice crystals bend or refract the light and form a circular ring with an angular diameter of 22 degrees. This is approximately the distance spanned between the tips of the thumb and pinky of your outstretched hand at arm's length. Although there are specialty books on the market almost any weather guide such as "Clouds and Weather" (one of the Peterson First Guides) by John A. Day and Vincent J. Schaefer discuss atmospheric phenomena. A very good source on the web with many photographic examples is the German Halo Workgroup which maintains an English language version of their site at http://www.meteoros.de/indexe.htm. Several years ago my family and I stepped off a plane onto the tarmac in Omaha on a sunny yet insufferably bitter Winter's day. The -18 degree Fahrenheit temperature and a stiff steady wind combined to produce a wind chill temperature of 80 degrees below zero! Glancing up at the sky on the walk to the terminal I saw an amazing sight. Instead of a single Sun there were six suns in the sky! The real Sun had five other suns surrounding as a result of a combination of phenomena related to ice crystals suspended in the air. There was a sun to the right and left, one above, and two below on either side. They were all situated at points around the solar halo and exhibited tinges of rainbow color. The two appearing on the right and left sides are called "perhelia" or "sun dogs." They appear on opposite sides of the Sun, to its left and right. The sun on top was actually just the brightest point of a phenomenon known as the "upper tangent arc" which gets its name by being tangent to the halo. The German web site has a good photograph showing the sundogs and this arc at http://www.meteoros.de/phaeno/ph8_4k.jpg. Not as bright as the sun dogs, the false impostors below the Sun form a 120 degree angle with it. Thus, these twins are known as the "120 degree parhelia." Sometimes near sunset or sunrise "sun pillars" can be observed. The observer sees a bright column of orange light either above or below the Sun when it is low on the horizon. Upper pillars may even be visible when the Sun is below the horizon. Sun pillars are a common site for commuters during the morning or evening drive when the sun is hugging the horizon and are caused by sunlight reflecting off the faces of the hexagonal ice plates. On a recent night I stepped out of my observatory and noticed what appeared to be several bright wide Auroral "spikes" extending straight up from the horizon for about 20 degrees. There were also other spikes involved with and extending above the awful glow of the dome of artificial light hanging above Westminster. Continuing to pan around the horizon there were other spikes which seemed to correspond with the light polluted cities of Eldersburg and Mt. Airy. As an astronomer a warning bell went off in my head. How likely is it to see northern lights along the southern horizon in the direction of Mt. Airy? Not very likely. Instead, what I was seeing was another form of sun pillar, except that it was caused by an unnatural illumination. Wasted light from artificial light sources over the horizon was being reflected off the bottom surfaces of suspended ice plates forming pillars of light. Although they were over the horizon the likely sources for the two brightest pillars is the light being beamed skyward from the rock crushing plant in Union Bridge and the Ski Liberty complex in Pennsylvania. Both locations consume Watts used for no other apparent reason than for lighting up clouds and the bellies of nocturnal birds. The direct effect of such wasted light is the strangulation of the marvelous light approaching from distant sources. Light from a distant galaxy from the combined light of a hundred billion brightly burning stars that may have started its journey as dinosaurs walked the Earth grows weaker during its lengthy journey through space. When this fossil relic of ancient light finally nears its final destination at the backs of our retinas and passes through the atmosphere it is suddenly and tragically vanquished by the spray of wasted photons from the unshielded light negligently beaming them upward where they do the least good and cause the most harm. For an explanation of natural and artificial pillars of light, see Spectrum Educational Enterprises' web page at http://www.islandnet.com/~see/weather/eyes/pillars.htm.