B Analysis and Theory

Whether astronomers take data from a ground-based telescope or have data radioed to them from space, they must then analyze the data. Usually the data are handled with the aid of a computer, which can carry out various manipulations the astronomer requests. For example, some of the individual picture elements, or pixels, of a CCD may be slightly more sensitive than others. Consequently, astronomers sometimes take images of blank sky to measure which pixels appear brighter. They can then take these variations into account when interpreting the actual celestial images. Astronomers may write their own computer programs to analyze data or, as is increasingly the case, use certain standard computer programs developed at national observatories or elsewhere. Often an astronomer uses observations to test a specific theory. Sometimes, a new experimental capability allows astronomers to study a new part of the electromagnetic spectrum or to see objects in greater detail or through special filters. If the observations do not verify the predictions of a theory, the theory must be discarded or, if possible, modified.