Radio telescopes (at first juryrigged World War II radars) were, perhaps, the first widely used non-optical astronomical telescopes. These telescopes are most notably responsible for our discovery of the cosmic microwave background (a Nobel Prize winning confirmation of the Hot Big Bang), and the discovery of pulsars (also a Nobel Prize winner). However, radio astronomy also plays a crucial role in our understanding of quasars, galaxies, and our own galaxy. Since radio has a much longer wavelength (millimeters to meters) than does visible light (0.4-0.7 micrometers), a completely different set of physical processes is responsible for their emission, so that looking in these two very different wavelength and energy regimes gives us two separate handles on what an object is really doing.
On the other end of the spectrum, we have X- and gamma- rays, (wavelengths of 0.1 nanometers down to 0.01 femtometers[!].) This very highly energetic radiation comes only from the hottest places in the universe. In X-rays, typical sources are accretion disks, which are formed by the matter swirling into a black hole. Just before the matter falls in, it is moving so fast (a fair fraction of the speed of light) and interacting so violently with its surroundings, that it is heated up to 10 million degrees and glows brilliantly in X-rays (if your stove were 10 million degrees, it would also glow brilliantly in X-ray, but at, perhaps, 1000 degrees, it barely glows in the visible). Gamma rays come from still more exotic places, where matter and light are exchanged rapidly (as with nuclear reactions). One such place produces violent bursts called gamma ray bursts. So energetic are these that they emit as much energy in just a few seconds as the sun will ever emit. Their nature is still not known, although several teams, using X-ray, optical, and radio telescopes are now able to track a burst for several days as it cools into longer wavelengths. The first such opporunity came in March, and vital but puzzling clues about the nature of the burst were revealed. Without gamma-ray telescopes, we never would have known about these, perhaps, the most luminous objects in the universe, at all.
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