Thanks to today's Google Doodle, we're reminded that Nov. 8 is the 115th anniversary of the discovery of the X-ray! If you do a Google search for "X-ray," it will turn up the usual suspects: A mock X-ray photo of Homer Simpson's head, a handful of articles and websites detailing the use of X-rays in medicine, and even art, like the image above taken by photographer Nick Veasy. What isn't as prominent and what some might forget is the role x-ray photography has played in our understanding of the Universe.
X-rays were discovered by Wilhelm Rontgen, a German physicist, in 1895. He was messing around with electromagnetic radiation, shooting an electron beam through a tube. Rontgen noticed that when his beam of radiation was turned on, a fluorescent screen in his lab starting glowing. He put his hand between the tube and the screen and saw his bones projected onto the screen. Just like that, X-ray photography was born!
Rontgen's first X-ray photograph was of his wife's hand. Today, medical doctors use X-rays to check for broken bones and locate swallowed pennies. In the same way, physicists detect X-rays coming from space, capturing images of celestial matter that, just like broken bones, human eyes alone could not see.
Stars, star systems, black holes and the remnants of supernovae are just some of the things in space that emit X-ray radiation. X-ray astronomers use telescopes in orbits high above the Earth to take pictures of high energy, high temperature cosmic objects like this X-ray image of our own Sun taken by the Hinode satellite. Scientists must use satellites because the Earth's atmosphere prevents x-rays from reaching the Earth's surface. (Though this is bad news for scientists, it's good news for the rest of us, since a prolonged bombardment of X-ray radiation can be harmful to humans.)
The Chandra X-Ray Observatory, in an elliptical orbit that ranges from 10,000 to 83,000 miles above the Earth, is another satellite spying on celestial X-ray emitters. The Chandra satellite took the image of two colliding galaxies at the top of this post and also the photo below of a suspected supernova.
X-ray telescopes uncover layers of phenomena whose visible spectrum signatures don't tell the whole story. They can detect gas left over from an exploded star (a supernova). They can 'see' radiation lurking just outside a black hole. They're high-orbit detectives who give scientists another set of eyes with which to see and study the Universe.