What is Observational Astronomy?

Updated: May 12

This branch of astronomy studies the universe by recording and collecting data from the observable universe. Traditionally humans observed the night sky with naked eyes before Galileo Galilei used the telescope to observe the universe. Hence, he is known as 'the father of observational astronomy. Observational astronomy has progressed steadily since then, with each advancement in telescope technology.


All truths are easy to understand once they are discovered; the point is to discover them. - Galileo Galilei

During old times, people categorized the sky in different parts using the shape of stars in a group - the constellations. They named each constellation based on the object they saw every day. More than 2,000 years ago, the Greek astronomer Hipparchus was the first to make a catalog of stars according to their brightness and this was the very beginning of tabulating the observed information.


Observational Astronomy

With time, telescopes developed and today we have different ways to observe the universe, by dividing it into the information received from various parts of the electromagnetic spectrum. - Visible/Optical Astronomy, Infrared Astronomy, Radio Astronomy, X-ray astronomy, Gamma-ray Astronomy, Extreme UV astronomy. Let's look into each one on them briefly.


1. Visible/Optical Astronomy

Many amateur astronomers continue to perform visible-light astronomy today, especially since that telescopes are considerably more generally available to the public than they were when they were originally created. Space telescopes, which are located outside of the Earth's atmosphere, are used to gather the finest quality images and data in the new age. Because the atmosphere is not interfering with the picture and observing the quality of the telescope, things may be studied in much higher detail, and considerably more distant or low-light objects can be observed.


2. Infrared Astronomy

The study of astronomical objects by using infrared light. This is relatively recent because in the 1930s infrared telescopes were developed in parallel with visible and ultraviolet telescopes. Infrared emissions are invisible to our eyes but can be seen with infrared or optical telescopes that capture even very cold objects such as interstellar dust clouds. Infrared telescopes and cameras that work in the infrared ranges of the electromagnetic spectrum are called near-infrared, mid-infrared, and far-infrared instruments.


3. Radio Astronomy

Radio astronomy studies celestial objects at microwave and radio wavelengths—the longest wavelengths of the electromagnetic spectrum. Radio astronomers use large radio antennas called radio telescopes to receive faint radio waves from the most distant objects in the universe. They analyze the massive amounts of data collected by telescopes. They convert the numbers into pictures. Colors are frequently assigned to numbers based on the amount of information they represent. Astronomers then combine the colors to create a picture, visualizing the data to reveal some of the properties of objects in the Universe. They also use radio telescopes to study nearby objects in our solar system, such as planets, asteroids, comets, and moons.


4. X-ray astronomy

X-ray astronomy is a branch of astronomy that deals with the detection and study of X-rays produced by astronomical objects. X-rays are high-energy electromagnetic radiation with wavelengths shorter than those of visible light, but longer than those of gamma rays. Unlike gamma rays, the wavelength of X-rays is determined by the energy level of their associated electrons. Because X-rays are absorbed by the Earth's atmosphere, X-ray detection instruments must be carried to high altitudes by balloons, sounding rockets, and satellites. X-ray emission is expected from astronomical objects containing extremely hot gases with temperatures ranging from a million to hundreds of millions of kelvins (K) (MK). The two main sources of X-rays are supernova remnants and active galactic nuclei. X-ray telescopes can observe in different bands depending on how much energy photons have, for example, soft X-ray, hard X-ray, or extreme ultra-hard spectrum.


5. Gamma-ray astronomy

Gamma-ray astronomy is a branch of astronomy that deals with the detection and study of gamma-ray produced by astronomical objects. Gamma-ray telescopes study high-energy astrophysical systems such as stellar coronas, white dwarf stars, neutron stars, black holes, supernova remnants, galaxy clusters, and diffuse gamma-ray background radiation found along the plane of the Milky Way Galaxy. Because the Earth's atmosphere shields the majority of gamma rays, most observations are carried out by high-altitude balloons or spacecraft like X-ray detection. Most gamma rays produced by solar flares and the Earth's atmosphere are in the MeV range, however, it is now recognized that solar flares can also produce gamma-rays in the GeV range. It was previously thought that gamma-rays in the GeV range did not originate in the Solar System.


6. Extreme UV astronomy

During the early years of space astronomy, research in the extreme ultraviolet (EUV) band of the spectrum was dismissed as unattainable, owing to the false belief that radiation in this band would be absorbed by the interstellar medium. Observations from sounding rockets and limited-term orbital spacecraft in the 1980s demonstrated the field's promise, leading to the deployment of two spacecraft specialized to EUV astronomy: the UK Wide Field Camera and the Extreme Ultraviolet Explorer. Although the instrumentation in these missions was restricted in comparison to other branches of space astronomy, it produced unique and far-reaching results. New knowledge on the solar system, star chromospheres and corona, white dwarf astrophysics, cataclysmic variables, the interstellar medium, galaxies, and clusters of galaxies were among them.

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