A Universe of Galaxies

When the earliest astronomers and philosophers looked up at the night sky, they never could have imagined a sight like this.

What if I told you there are only four single stars in this image?

That’s right. Four.

The rest are whole galaxies, full of billions of stars.

You can tell the foreground stars from the galaxies by the diffraction spikes–astronomer speak for those four bright spikes of light. Can you find them?

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What is a Nebula?

Backyard_photo_of_the_Orion_Nebula.jpg

What’s a nebula?

Well…you’re looking at one.

Okay, okay, I know. You want to know what that actually is. You want to know why it’s there. You want to know why there are colors in space…and why you’ve never noticed such a thing in your own night sky before.

Nebulae are the stuff between the stars. They’re the galaxy’s backstage. They’re the only visible evidence of a vast expanse of gas and dust between the stars, completely invisible to the human eye, called the interstellar medium.

Nebulae are the sites of star birth. Planets form from the dusty particles present in these glowing space clouds. They’re the galaxy’s way of replenishing itself. And they’re pretty cool to look at, too.

But how come they look the way they do?

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