The Night Sky |
Poets say science takes away from the beauty of the stars ~ mere globs of gas atoms. Nothing is "mere." I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination ~ stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern ~ of which I am a part ~ perhaps my stuff was belched from some forgotten star, as one is belching there. Or see them with the greater eye of Palomar, rushing all apart from some common starting point when they were perhaps all together. What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?
When we think of astronomy, we tend to think of the night sky because that is when the stars are visible. However, many astronomical observations can go on during the day, including those of the Sun and Moon, some planets, and many activities dealing with radio waves instead of visible light.
Still, the night sky embodies the essence of astronomy, and it is this star-studded darkness that first elicited in ancient people the awe and wonder that we feel even in our modern world. With it, astronomy is one of the most wondrous of pursuits. Without it, it is about as appealing as cold oatmeal.
Lacking all the many ways we have to wile away the evening hours, the ancients spent much more time gazing
at the heavens, and telling stories around the campfire. Do you remember lying on the grass on a lazy summer afternoon and imaging animals and other things in the clouds? The stories of
constellations are a bit like that, except that the constellations were there -- essentially changeless night after night, year after year.
Orion (left) appears the same today as it did back then. We may not be able to see the great Warrior or Hunter that many ancient people imagined, but the distinct rectangle of four bright stars straddled by the three-star "belt" is hard to mistake. The only real aspect that changes is the time of night in which we can view it, which is seasonal, and whether it is tilted back, upright or forward.
An interesting point to note is that the constellations are not all visible at the same time, but rather are seasonal. Most affected those constellations located along or near the ecliptic (the Sun's apparent path through the year). When the Sun is in the direction of the constellation, then obviously the stars are not going to be visible. As the Earth moves around the Sun throughout the year, it passes in front of various constellations, hiding them from view. If you were to watch from sundown to dawn in a clear sky, roughly 2/3rds of all the constellations visible from your latitude could be seen one any given night. The other one third or so are too close to the Sun to be seen. But as the Earth's motion changes the direction in which we see the Sun, certain constellations are drowned out while others emerge from the glare. (Diagrams on pages 17 & 18 in your book illustrate this -- MUST CONFIRM.)
Various constellations are oriented best for viewing at different times of the year. Orion is best seen in late Winter and Spring. Scorpius, which is opposite Orion in the sky, is best seen from late Summer through Fall.
In addition to the stars and constellations, of course, there is often the Moon, which because of its motion around the Earth, is visible at any given time of night about half the nights of the month. Like the Sun, the Moon is above the horizon and visible about half the time, and below the horizon the other half. However, since its motion around the Earth is much faster than the Earth's motion around the Sun, you can't expect to see the Moon at the same time every night.
The planets, too, move through the heavens at their own pace, slowly drifting against the background of the vastly more distant stars. However, their motions are slow enough that they generally don't appear to move much, relative to the stars, from night to night. How do you tell a star from a planet? Well, if you have a star chart and can identify a constellation, say Taurus the Bull, and you find that there is an extra "star" in the constellation, it most likely is a planet. Also, planets tend to glow with a steadier light than stars -- that it, planets don't twinkle much. Stars, especially bright stars such as Sirius, may flicker and twinkle madly because of the effect of Earth's atmosphere. This is especially true when the star appears near the horizon, and its light must pass through thicker layers of air. Planets, on the other hand, are far less affected by the Earth's turbulent air, primarily because planets appear as much larger objects than do stars.
On any given night after midnight, a single observer can expect to see 6 or 7 meteors streak across the sky. During certain times of the year there are more than usual, events that are a bit misleadingly called meteor "showers." Usually the most prominent of these is the Perseids in the second week of August, and the Geminids in mid-December.
Of course, there are other things that are seen from time to time in the sky, including the Aurorae (chapter 4), and occasional anomalous sightings of Unidentified Flying Objects or UFOs. This is not the place to discuss UFOs or the merits of various observations. Just keep in mind that because the observer can not identify them, it does not mean that they are alien spaceships!
For now, try the activity. If possible, go out under the real sky some evening and try to imagine the vastness of space. Capture the wonder that humans have always held for the night sky.
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