What's An Image?
   


















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.  Let's see what celestial objects look like in other parts of the spectrum.... 
   




   




























                   

  All four pictures on the left 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 is 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 energy, 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.
                




















 







 
  







 
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,  click on the Chandra image above and 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..