Whats so special about X-ray and gamma-ray spectroscopy?
One reason is that, sometimes, X-ray spectroscopy is simpler to interpret than optical spectroscopy. This is because, at X-ray temperatures, atoms are highly ionized (most of the electrons have been taken away from the atoms), leaving only a few electrons per nucleus. This makes theoretical calculations much easier! Thus it is, in principle, much easier to relate the strengths of X-ray lines to, for example, the abundances of various elements. A more important reason is that there are many classes of astronomical objects that contain high temperature gases (at millions of degrees K). At these temperatures, more of their energies are radiated as X-rays (both continuum and lines) than at other wavelength ranges, so it makes sense to observe them in the X-rays. Such hot gases can be found, for example, in the corona of the Sun: the observation of the Solar corona is very important because Solar flares and other activities there can affect satellite communication links and the health of as
