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So, what is an image?

Seeing Through Different Eyes | What is an image? | I'm not lost . . . I've got a map!
So what if the Earth is round?! | A new wrinkle . . . the third dimension. | Earth vs. the Center of the Galaxy


When we look out into space, what do we see? We see what the human eye allows us to see, which is optical light. You know, the colors of the rainbow. In reality, there is a lot more to the light spectrum than our eyes are capable of seeing. And this other light often provides valuable clues about the nature of the objects in the sky.

Crab Nebula
The Crab Nebula
Enlarge Image
Let's see what celestial objects look like in other parts of the spectrum....

All four pictures on the right are of the same object, the Crab Nebula. They all look different don't they? The optical one is what our human eye can see (the visible spectrum). The other three are at different wavelengths of light. Isn't it fascinating how much our human eye misses out on? Since we can't "see" x-rays, radio waves, and infrared radiation except with instruments (usually telescopes) other than our eyes, we have to use "false color" to represent the images. What this does is take the x-ray, infrared or radio energy, and assign these wavelengths to colors that we can see, thereby providing us with a nifty way to "see" these objects as if our eyes could do so.

You may think that an image is just the collection of light from an object, but this is far from the case. You will learn that by looking at WHEN the light arrives at the telescope and with WHAT ENERGY, a fantastic amount can be learned about many objects in the sky; not only stars, but galaxies, and bizarre objects like white dwarves, quasars, and supernovae. In the following pages, you will see what we can learn by looking at X-rays using NASA's Chandra X-ray Observatory. You will be using real data that scientists actually use when they investigate the nature of our universe. Chandra orbits the Earth and captures pictures like the one in the top left above.

software
To begin, you need to install some FREE software that will allow you to use the Chandra data. Not only is this software powerful, it is a LOT of fun to use. So, follow the instructions on the Chandra home page to install the software and go through the tutorial. Return here to start your journey of discovery about the x-ray universe.

The first thing we want to explore is where these objects are in space, and how we can find them in the sky. We don't want to get lost in space.... To find our way around, we will see how your knowledge of maps on the Earth can be applied to the sky. Let's begin!
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