How Are Galaxies and Constellations Alike and Different?
Looking upon a clear night sky, various shapes outlined by stars appear while the band of our galaxy dominates our view. Well, that view is not as much now as in past years thanks to the spread of urban areas and their light, but nonetheless constellations and galaxies are there. The qualities that distinguish a galaxy and a constellation are important to identify as one takes the cosmos into scope.
Before modern astronomy, a constellation was a shape in the sky that reflected a character from mythology. Various cultures had their own labels for those creatures in the sky, but it is from the Greek/Roman tradition that the Arabic astronomers of past made common nomenclature. These shapes are made of stars, hot balls of plasma that radiate heat from several thousand degrees Kelvin to millions of degrees. While it may appear from our viewpoint on the Earth that these stars are in the same area of space and distance, their actual distance from us varies with each star. As modern astronomy advanced, the areas of a constellations influence was murky. Eventually the constellations would be given a specific area of space that was under their domain. Today, 88 constellations are recognized by astronomers.
Until the 1930s, galaxies were not known as such, but as patches of stars residing in our galaxy. But when the distance to these patches was discovered, it quickly became apparent that they were a new type of object. These objects contain billions of stars that orbit around what is called a super massive black hole, a singularity that has a mass equivalent to millions of stars and absorbs matter, even light. Some galaxies have arms, where local clusters of stars rotate around the center at the same rate. Older galaxies are elliptical, containing no discernible arms. Others are completely irregular, perhaps the result of a merger of galaxies. Galaxies are held together by dark matter, a not fully understood substances that does not interact with light but has gravitational interactions.
Galaxies and constellations have one item in common: stars. Other than that, they are separate objects. Sometimes a galaxy may appear to reside inside a constellation, but this is because of our vantage point on Earth. The distance between them is millions of light years at times. Someday, constellations will no longer be in their shape that we take for granted, nor will the galaxies be in their place, for the universe is expanding and changing as time progresses forward. Our place in the cosmos moves and it moves in return. Who knows what possible constellations of the future there will be.
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© 2011 Leonard Kelley