Observational Astronomy
In modern era, astronomy has many different parts to study with. In astronomy, the main source of information is the detection and analysis of visible light and other electromagnetic radiations. The main branch of astronomy, i.e. observational astronomy is further bifurcated in many more different branches such as Radio Astronomy, Infrared (IR) Astronomy, Ultraviolet (UV) Astronomy and many more based on the observed electromagnetic spectrum, most widely known as EM Spectrum. There are some parts of the EM Spectrum that can be observed from Earth, while other parts can be observed from space.
The main categories of observational astronomy are as follows:
• Radio Astronomy:
Radio astronomy deals with the wavelengths larger than one millimeter. Radio Astronomy studies the observed radio waves that can be treated as waves rather than photons. Most of the radio waves observed are produced due to oscillation of electrons around magnetic fields. And the spectrum emitted is observed as a radio wave.
• Infrared Astronomy:
Infrared Astronomy studies the detection and analysis of infrared radiation. Since most of the IR radiation is absorbed by the atmosphere of Earth, hence infrared observatories are located at high places or more preferably in space.
• Optical Astronomy:
Optical astronomy is the oldest type of observational astronomy. It is also called the visible light astronomy. It includes imaging (picture is made of the object), photometry (the amount of light coming from an object is measured), spectroscopy (the distribution of light with respect to the wavelengths is calculated) and polarimetry (the polarization state of the light is measured).
• Ultraviolet Astronomy:
Ultraviolet astronomy deals with the studies of ultraviolet radiations. Ultraviolet astronomy is best for thermal emission or spectral lines. The main sources of UV rays are planetary nebulae, active galactic nuclei and supernovas.
• X-Ray Astronomy:
X-ray astronomy deals with the study of celestial bodies which emits X-rays. X-ray emission can be produced due to synchrotron emission (electrons oscillating around magnetic field lines), thermal emission from thin gases which is widely known as bremsstrahlung radiation and blackbody radiation. Like Gamma rays, X-rays are also absorbed by atmosphere, they are observed from high altitude by using rockets and spacecrafts. X-ray emission can be seen in pulsars, binary stars, clusters of galaxies and active galactic nuclei.
• Gamma Astronomy:
Gamma astronomy deals with the Gamma radiation in the universe. It studies the celestial objects which are at shortest wavelengths of EM spectrum. Gamma rays can be observed by satellites or by Gamma telescopes. The Gamma ray bursts are the richest source of Gamma ray emission. These Gamma ray emissions can be seen in pulsars, neutron stars and black holes.
The other main division of observational astronomy is not based on EM spectrum but on other specifications. Divisions that do not deal with EM spectrum include the following fields:
• Neutrino Astronomy:
With the help of neutrino detectors in specially designed observatories, it deals with the observation of celestial objects that emit neutrino particles. These neutrinos are produced by the nuclear reactions in stars and supernova explosion. But most of them are being destroyed as they last for fraction of a second, only a few of them reaches to earth and can be captured.
• Planetary Astronomy:
Planetary astronomy, also called as planetology, deals with the study of planets, planetary system and the solar system. Planetary astronomy studies the planets of solar system, their moons and the radiations of solar system. This study proves very essential for the space missions that in solar system.