Joanna Pitsihoulis, Age 11, Of Charlotte, N.C., for her question:
What is beyond the galaxy?
Our star studded galaxy spans a circle some 80,000 light years wide, but it is a mere speck of dust in the stupendous universe. Einstein claimed that this universe is expanding. This may be true. But it certainly is true that our knowledge of the universe is expanding and at a great rate.
The milky way gives us a hazy picture of the galaxy which is our home in the heavens. Beyond it stretches the universe, the cosmos, to distances beyond the imagination in all directions. And the cosmos is populated with teeming numbers of galaxies similar to our own. Three of these outer galaxies, these extragalactic star systems, are faintly visible to our eyes.
Two can be seen from the southern hemisphere as pale blurs of light. The third is a hazy glow in andromeda, a constellation of our fall and winter skies. Astronomers long suspected that cosmic space is strewn with other galaxies, and the far seeing telescopes prove this to be true. The count of the cosmic population increases as more and more powerful telescopes and radio telescopes are made.
In 1932, 500,000 galaxies had been identified. Now we have the big 200 inch telescope that probes the cosmos on all sides of us to a distance of 1 billion light years. Some of its photographic plates of the stupendous cosmos look like our starry skies, but each speck of light is a vast star system similar to our entire galaxy. Here and there they are clustered in fairly close groups, but in the main the extragalactic star systems are strewn fairly evenly throughout the known cosmos.
Most of them are lens shaped with thick star crowded centers and thinner edges. Many are spiral nebulae, like our own galaxy, with starry arms coiling out and around from their central nuclei. Some are elliptical nebulae, oval systems with no crowded centers. Some are irregular systems with no definite shapes. On the average, these swarming galaxies are separated by about 4 million light years and where they end nobody knows.
When we know just where to look, our eyes can see the Andromeda nebula, as a hazy blur. Through a good telescope, we see only the bright center of an outer galaxy. The thinner edges and the spiraling arms can be seen only on telescop’s plates. These plates also reveal individual stars like those that populate our own galaxy.
Our best telescopes cannot probe to the outer limits of space, and if they could our minds could not grasp it. If we reached the edge we would then wonder what is beyond it, for that, too, is part of the universe. We know that the wide reaches beyond our galaxy are strewn with billions and perhaps more billions of star systems and that many of them are dazzling spiral nebulae, very much like our very own home in the heavens.