1000 Things You Didn’t Know About The Universe #2: Galaxies are Everywhere

Welcome to a new series of posts that will characterize 1000 amazing facts about the Universe.  There is so much out there that we have yet to learn, and every day, astronomers across the globe are using their research to reveal the deepest secrets of the cosmos.  This series will look at the strangest, coolest, most exciting facts that we have discovered in hundreds of years of modern science.

Fact #2: There are more Galaxies than you could possibly count.

Our night sky is jam-packed with stars.  If you’ve ever left the city to go far beyond the reach of the lights of civilization, you’ll see a sky full of amazing stars of all sizes and colours, forming intricate shapes that our brains attach meaning to.  But this is just a small fraction of the Milky Way Galaxy, a giant island of stars, gas, dust, and other strange objects, which contains somewhere around 400 Billion stars.


You may have heard about other galaxies in the universe that can be seen with keen eyes and a decent telescope.  A few hundred of them are targets for amateur and professional astronomers alike.  But if we step a bit further into the vast darkness of space, we find more galaxies than one could possibly view in a lifetime.

In 1995, the Hubble Space Telescope was pointed to a supposedly empty part of the sky, in the constellation Ursa Major.  It took 342 exposures over ten days, in an area of sky the size of a grain of sand held at arm’s length.

Hubble Ultra Deep Field Credit: NASA, HST

The result was spellbinding.  In the image above, every dot you can see is not a star, but a galaxy, each containing hundreds of billions of their own stars and countless more planets, moons, asteroids, and comets.  And this was simply one tiny area of the sky.

To verify if this was the same everywhere, and not just a lucky shot, the process was repeated for the southern hemisphere, and named the Hubble Deep Field South.  The result was the exact same; a tiny area of sky containing thousands of individual galaxies.  This provided strong evidence that the universe was homogeneous, roughly the same in every direction.

This means that if we took our grain of sand and pointed it anywhere in the sky, if we could zoom in and see what Hubble sees, we should see thousands upon thousands of galaxies no matter where we look.  A back of the envelope estimate suggests that the observable universe contains over 100 billion Galaxies, each one containing hundreds of billions of stars.  Our universe is full of stuff, and the possibilities for life to form are endless.

But that’s another story…

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