Linda Johnson. age 13 of Bellevue. Wash
How big. is the Galaxy?
The size of the Galaxy is immense! We shall have to exercise our imaginations to grasp it. Letts begin by imagining a ‑mile's distance up in the sky. Now stretch that to a thousand miles. Your imagination has a now taken you/twenty‑fifth of the distance to the moon. Go on up and up until you have imagined yourself a million miles closer to the sun. You are now way out in space‑with the black's star‑studded skies all around you. Yet the sun our nearest stars is still about 92 million miles away.
To grasp the immense size of the Galaxy we must think of these distances in light years. This is the distance: light travels in one year. It is million roughly six million miles. The altars of the Galaxy pare all around us. A few are as close as four and a half to eight and a half light years: While the light from some stars in the Galaxy takes thirty light years to reach us ‑ always. traveling at the breakneck speed of about 186,000 miles a second.'
The shape of the vast system of stars is rather like a pinwheel:. It is round. somewhat flat. with the thickest section in the center. The Solar System is about two thirds from the center of the Galaxy. Here the stars are fewer sand more scattered. Yet sometimes we can look up thirty light years of distance and see the hazy light around the heart of the vast system of stars.
On a very clear nights. you may see a pale haze of light looping over the heavens.. This; is the Milky Way. It is made of distant stars towards the center of the Galaxy. There are thousands of them. We cannot see them separately without a telescope. The light from these glowing suns merges and reaches us as; a milky haze. Light from some of them has been traveling towards us from maybe thirty years or more.
Maybe your imagination is now ready for the dimensions of the giant pinwheel of stars. From rim to rim. right through the shining center. the Galaxy measures about 100,000 light years. Multiply this figure; by six million million. You then have the diameter of the Galaxy in ordinary miles.
It is followed. by seventeen zeros. At its thick‑at point. in the center the Galaxy is about: 10 light years away in miles. this is 6followed by thirteen zeros.
This is roughly the size of our vast starry Galaxy. You would think it big enough to fill the whole heaven. Not at all. Around it in all directions stretch the vast reaches of space. And our Island Universe of stars is not the only one of its kind. For there are many many Island Universes or Galaxies like our own.
Galaxies are photographed by our most powerful telescopes. Thousands of them have been spotted.. some of them millions of light years away. Many of them are shaped very much like our own. They are photographed eat various angles. Some taken from the rim. look like lenses others taken from the flat side. look like starry plates. Our Galaxy is a big one. For a time we thought it to be the biggest. Now it is thought that others as big. or even bigger exist in the heavens.