Awesome Size

4. What was discovered in the 1920’s?

⁴ In recent centuries astronomers who scanned the heavens with early telescopes noticed some fuzzy, cloudlike formations. They assumed that these were nearby clouds of gases. But in the 1920’s, as larger, more powerful telescopes came into use, these “gases” were found to be something far more immense and significant: galaxies.

5. (a) What is a galaxy? (b) What does our Milky Way galaxy include?

⁵ A galaxy is a vast group of stars, gas and other material rotating around a central nucleus. Galaxies have been called island universes, for each one of them is in itself like a universe. For example, consider the galaxy we live in, which is called the Milky Way. Our solar system, that is the sun and the earth and other planets with their moons, is part of this galaxy. But it is only a very tiny part, for our Milky Way galaxy contains over 100 billion stars! Some scientists estimate at least 200 to 400 billion. And one science editor even stated: “There could be as many as five to ten trillion stars in the Milky Way galaxy.”⁠²

6. How vast is the distance across our galaxy?

⁶ The diameter of our galaxy spans so vast a distance that if you could travel as fast as the speed of light (186,282 miles a second) it would take you 100,000 years to cross it! How many miles is that? Well, since light travels about six trillion (6,000,000,000,000) miles in a year, multiply that by 100,000 and you have the answer: our Milky Way galaxy is about 600 quadrillion (600,000,000,000,000,000) miles in diameter! The average distance between stars within the galaxy is said to be about six light-years, or about 36 trillion miles.

7. What estimates have been made of the number of galaxies in the universe?

⁷ It is almost impossible for the human mind to comprehend such size and distance. And yet, our galaxy is just the beginning of what is in outer space! There is something even more staggering. It is this: So many galaxies have now been detected that it has been said they “are as common as blades of grass in a meadow.”⁠³ About ten billion galaxies are in the observable universe! But there are many more beyond the range of today’s telescopes. Some astronomers estimate that there are 100 billion galaxies in the universe! And each galaxy may contain hundreds of billions of stars!

Clusters of Galaxies

8. How are galaxies arranged?

⁸ Yet, there is more. These awesome galaxies are not scattered haphazardly in space. Instead, they are usually arranged in definite groups called clusters, like grapes in a bunch. Thousands of these galactic clusters already have been observed and photographed.

9. What is included in our local galactic cluster?

⁹ Some clusters contain relatively few galaxies. Our Milky Way galaxy, for example, is part of a cluster of about twenty galaxies. Within this local group, there is one “neighbor” galaxy that can be seen without a telescope on a clear night. It is the Andromeda galaxy, which has a spiral shape similar to ours.

10. (a) How many galaxies may be in a cluster? (b) What are the distances between galaxies, and between clusters of galaxies?

¹⁰ Other galactic clusters are made up of many dozens, perhaps hundreds or even thousands, of galaxies. One such cluster is thought to contain about 10,000 galaxies! The distance between galaxies within a cluster may average about a million light-years. However, the distance from one galactic cluster to another may be a hundred times that. And there is even evidence that the clusters themselves are arranged in “superclusters,” like bunches of grapes on a vine. What colossal size and brilliant organization!

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A typical spiral galaxy

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Our solar system, in square above, is dwarfed when compared with our Milky Way galaxy

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The Andromeda galaxy, similar to our own Milky Way, is only a small part of the awesome universe that some say contains about 100 billion galaxies