Astronomy 101

Observational Astronomy part 1

In astronomy, the main source of information about celestial bodies and other objects is the visible light or more generallyelectromagnetic radiation. Observational astronomy may be divided according to the observed region of the electromagnetic spectrum. Some parts of the spectrum can be observed from the Earth's surface, while other parts are only observable from either high altitudes or space. Specific information on these subfields is given below.

Radio astronomy

The Very Large Array in New Mexico, an example of a radio telescope

Radio astronomy studies radiation with wavelengths greater than approximately one millimeter. Radio astronomy is different from most other forms of observational astronomy in that the observed radio waves can be treated as waves rather than as discrete photons. Hence, it is relatively easier to measure both the amplitude andphase of radio waves, whereas this is not as easily done at shorter wavelengths.

Although some radio waves are produced by astronomical objects in the form ofthermal emission, most of the radio emission that is observed from Earth is seen in the form of synchrotron radiation, which is produced when electrons oscillate aroundmagnetic fields. Additionally, a number of spectral lines produced by