Taking a piece of heat from a heat produces X-rays if this action is done empty. A team of researchers from the University of California has demonstrated this and made it known in the journal Nature.
A warmer was put to unstick in a vacuum chamber (collected in another roll) and saw that the heat emitted X-rays at the time of separating from the wrapper. It is called triboluminescence, as in the case of zeal, to the energy that comes off when crushing, rubbing or scraping a solid often a crystal.
Scientists were also able to demonstrate that the amount of rays emitted was sufficient to perform the X-ray of a finger of one of them. In the image you can see the vacuum chamber with heat inside, the hand of the scientist and the radiograph made.