Abstract:
Essentially all information about astronomical objects outside the solar
system reach us via light, i.e., the electromagnetic radiation. White light is
composed of many wavelengths which are not resolved into their different
colors. Monitoring white light gives the positions of objects in the night sky.
It can be used to construct maps of stars and galaxies and also be used to
plot the movements of heavenly bodies such as comets through the night sky.
Using instruments with low resolving power, it is possible to separate the
light arriving at Earth into broad band colors. Colors of celestial bodies
give information about their temperature. For example, blue stars are hotter
than red ones; objects that emit X-rays, such as the solar corona, are very
hot, whereas cold objects may only emit light of very long wavelengths such
as radio waves. The most detailed astrophysical information is only obtained from high-
resolution studies which involve detecting the light arriving at the earth as a function of its component wavelengths.
