How to focus an X-ray

This video shows Curtis Odell explaining how X-ray telescopes focus X-rays.

Visit the Suzaku Educational DVD page for more information on this video and to view other clips from the DVD.

A telescope, at its heart, is a device to collect light and deliver that light to a detector, no matter what type of light it is designed to observe. In order to capture and focus X-rays, “grazing incidence” optics must be used. X-rays are so energetic (and have such a small wavelength) that they tend to pass through most matter. Mirrors are no different. Most of the X-rays in a beam shot directly at a mirror would simply pass right through. Traditional designs of telescopes, then, just don’t work for X-ray astronomy.

However, if an X-ray encounters a mirror at a “grazing incidence”, i.e. if it just glances the surface of the mirror, then it will bounce, behaving just as an optical photon would.

Grazing incidence
Illustration of grazing incidence. X-ray telescopes require that the X-ray photons encounter the mirror at a “grazing incidence”, where they just glance the surface. The scale in this image is exaggerated, as the angle of incidence (the angle between the mirror surface and the X-ray) would be shallower.