The study of composition, motion, and other related facts is called Astronomy. It is not an experimental science. The reason is that we can’t control or change the particular occurrences of the heavenly bodies of the nature. So we can say it as an observational science. These occurrences can’t be managed or artificially created in the laboratory because these processes are non-repeatable. During these processes the factors like temperature, pressure etc are extremely high. So, maintaining such high conditions in the laboratories may be very risky.
If we have the urge to collect some info about these heavenly bodies of nature then we have to study about the electromagnetic radiations coming from them.
The range of these starts from very small range i.e. Gamma rays and extends up to long range radio waves. The atmosphere that is making a surrounding around us is absorbing and reflecting back lots of radiations. Most of these absorbed and reflected radiations are those which are emitted by the heavenly bodies. There are two main reasons, radiations of which have the capability to reach us. These are also called the two windows of the astronomy. The radiations which reach the earth are of different ranges, which are discussed below:
• Radiations of this region called as optical window of astronomy have wavelength starting from 4 X 10 -7m to 8 X 10 -7m.
• The other region is called as radio window of astronomy. The waves present in this region have wavelength of 8mm to 17m.
