A study of celestial objects and phenomena is known as Astronomy. The professionals who pursue the education of Astronomy are called Astronomers. It is a natural science which applies mathematics, physics, and chemistry. In this study, the explanation of the origin of celestial objects, phenomena, and their origin is covered. The major objects of interest are moons, stars, galaxies, and comets. It also includes supernova explosions, gamma-ray bursts, pulsars, quasars pulsars, and cosmic microwave background radiation. There is a related but distinct subject which is the study of the universe as a whole, physical cosmology.
Astronomy is one of the oldest studies and natural sciences as we can take evidence from recorded history like Babylonians, Greeks, Nubians, Maya, Iranians, Egyptians, Indians, and many ancient indigenous people of America. They all performed methodical observations of the night sky. There are two branches of professional astronomy: Observational and Theoretical. In observation astronomy, the focus is on the acquisition of data from observations of astronomical objects for analysis by using basic principles of physics. In theoretical astronomy, the focus is oriented towards the development of computer or analytical models for describing astronomical objects and phenomena. Both these branches complement each other as theoretical astronomy helps to explain observational results and observations are used to confirm theoretical results. It is one of the few sciences in which an active role can be played by even amateurs. Amateur astronomers contribute to the discovery and observation of transient events and many other important astronomical discoveries like the finding of comets.
Observational astronomy is further classified into 6 categories as per the corresponding region of the electromagnetic spectrum:
Radio Astronomy: In this category of astronomy, radiation with wavelengths greater than approximately one millimeter outside the visible range is used. This type of astronomy is different from most of the other categories. In this study, the observed radio waves can be treated as waves rather than as discrete photons. Therefore, it becomes relatively easier to measure both the amplitude and phase of radio waves. This can be easily done at shorter wavelengths.
Infrared Astronomy: This study is founded on the bases if detection and analysis of infrared radiation, wavelengths which are longer than the red light, and outside the range of our vision. It studies objects which are too cold to radiate visible light like planets, circumstellar disks whose light is blocked by dust. Clouds of dust are penetrated by the longer wavelengths of infrared. It allows the observation of young stars embedded in molecular clouds and the cores of galaxies.
Optical Astronomy: This astronomy is also called visible light astronomy. This is the oldest form of astronomy in which images of observations were originally drawn by hand. With the advancement of technologies in the late 19th and 20th century, photographic equipment was used for making the images. Modern images are made using digital detectors like charge-coupled devices (CCDs) and recorded on the modern medium.
Ultraviolet Astronomy: This category of astronomy employs ultraviolet wavelengths between 100 and 3200 A approximately. The atmosphere of earth absorbs the light at those wavelengths. This requires observations at these wavelengths to be performed from the upper atmosphere or from space. If you want to study thermal radiation and spectral emission lines from hot blue stars then this category of astronomy is best suited. This also includes blue stars in other galaxies which have been the targets of several ultraviolet surveys. In ultraviolet light, there are other objects also which can be commonly observed including planetary nebulae, supernova remnants, and active galactic nuclei.
X-Ray Astronomy: This type of astronomy uses X-ray wavelengths. The radiation of X-ray is produced by synchrotron emission, thermal emission from thin gases, and thermal emotions from thick gases. The observations of X-rays must be performed from high-altitude balloons, rockets, or X-ray astronomy satellites since these are absorbed by the earth atmosphere.
Gamma-Ray Astronomy: This field of astronomy observes astronomical objects at the shortest wavelengths of the electromagnetic spectrum. The rays of Gamma may be observed directly by satellites like the Crompton Gamma Ray Observatory. Gamma rays can be detected by the Cherenkov telescopes. This telescope instead detects the flashes of visible light which are produced when the atmosphere of earth absorbs the gamma rays.
Several tools are used by Theoretical astronomers like analytical models and computational numerical simulations. Each too has its particular advantage. If you want to have a broader insight into the hearty of what is going on then analytical models are better. If you want to know the phenomena and effects otherwise unobserved then numerical modes are used to reveal them. Theorists endeavor to create theoretical models and predict observational consequences of those models from the results.
There are various sub-fields also of Astronomy:
Astrophysics: This branch of astronomy employs the principles of physics and chemistry to ascertain the nature of the astronomical objects rather than their positions motions in space. In this branch, the objects which are studies are the Sun, other stars, galaxies, extrasolar planets, interstellar medium, and the cosmic microwave background.
Solar Astronomy: The most frequently studied star at a distance of about eight light-minutes is the Sun which is a typical main-sequence dwarf star of stellar class G2 V. The sun is about 4.6 billion years old. There is a core region at the center of the sun which comprises a volume of sufficient temperature and pressure for nuclear fusion to occur. Thereisa radiation zone above this core where the plasma conveys the energy flux by means of radiation.
Astrobiology: It is an interdisciplinary scientific field which is concerned with the early evolution, the origins, distribution, and the future of life in the universe. This study focuses on the question of whether extraterrestrial life exists. If it does, then how can humans detect it. This study makes use of biophysics, molecular biology, biochemistry, astronomy, chemistry, physical cosmology, exoplanetology, and geology for the investigation of the possibility of life on other worlds. This study also helps recognize biospheres.
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By: Madhuchanda Saxena
Posted By - Assistant Editor