X is for X-ray

Finally, an AtoZ blog entry where I don't have to stretch to find an entry.

We've talked a bit about the electromagnetic spectrum during the A to Z--Radio, Infrared, Visible (Optical) and Ultraviolet--because light is primarily the only tool we have to explore the universe.

While other bloggers are really pushing it to find something for the letter X, here's something that comes naturally to astronomers: X-rays

We all know about X-rays for their medical uses: broken a bone or been to the dentist, chances are you had an X-ray photograph taken.

X-rays are cool because they can penetrate certain types of matter and show us other types. This is because they're highly energetic. Naturally, this is a good thing for astronomers. We like looking at high-energy things.

X-rays were discovered in 1895 by Wilhelm Röntgen. Here's his original paper: German,  English Translation

"Hand mit ringen," Will said.
His wife said, "I have seen my death!"  Drama queen.

In fact, X-rays are often called Röntgen rays. What did Wilhelm Röntgen call them?  X-rays, with X standing for "mysterious", because he really wasn't sure what they were at first. Eventually he and a few scientists figured it out.  A few early articles about Röntgen's mysterious X-rays.

And, like any other scientist that thought science stuff was nifty, he played around with it, and even freaked his wife out by using her hand as a guinea pig by taking the first X-ray photograph.

This was fascinating, as it's really the image of an X-ray shadow, as the minerals of the bones block out the X-rays. Lead is also good for blocking out X-rays.

So, what makes X-rays so useful for astronomy?

Remember how stars come in different colours, depending on how hot they are?  If you boost the temperature of an object in outer space to waaay hot (more than a million Kelvin), its peak colour goes on beyond blue all the way up into X-rays.

This makes X-rays really useful for detecting high-energy events and objects.  Neutron stars and accreting black holes emit X-rays. Supernovae emit X-rays. (Stars emit X-rays, as they emit through the whole EM spectrum, though not to the same degree the Really Powerful Stuff, like active galactic nuclei, does.) Want to know where all the moving and shaking is happening in the universe?  Look for the bright X-ray spots.

Now, X-rays are absorbed by our atmosphere (thankfully), so any X-ray observatories need to be in orbit, like the Chandra X-Ray Observatory.

Here's some cool pictures taken in X-ray:

Looks very different from the hand mit ringen, as these are not images of the shadows of X-rays, but rather the emissions of X-rays. That's why they're so bright.

______________________________
Her Grace once calculated how much X-rays she emitted. Answer: not much.