India’s first space observatory, the Astrosat, turned 6 years old

Five years in space India’s first space observatory, the Astrosat.

In a Bengali home, a child’s five-year-old birthday is often celebrated with pomp and circumstance. I don’t know if there is that customers in all of India. However, Astrosat’s five-year anniversary is celebrated with great fanfare last week. To mark the occasion, ISRO organized a three-day international science conference on January 19-21.

The meeting is online due to the emergency situation. Scientists from home and abroad described what they have observed using astronauts. What new information has been revealed about various cosmic objects.To understand what Astrosat is and why ISRO build it in ten years of effort. A cost of around Rs 178 crore. we need to look at the history of astronomy. During World War II, many improvements are make in radio wave detection technology to build high-quality radars.

After the war, astronomers used that technology to detect the radiation of radio waves from cosmic objects. The same way, the use of advanced rocket technology to install cosmic X-ray radiation. In short-term rocket flight with the introduction of X-ray wave detectors began in 1950. In 2002, Ricardo Zacconi is awarde the Nobel Prize in Physics in recognition of his pioneering role in X-ray astronomy.

Astrosat satellite
photo credit: isro

Not only that, astronomers realize that the light we see with our eyes (visible light) is a wavelength of ‘light. That is, electromagnetic waves, such as infrared, microwave, radio, and light of shorter wavelengths. Such as ultraviolet, Gamma-rays, etc. are also being regularly radiate from various cosmic objects. Properly identifying the light of all these wavelengths, will be much easier. More complete to determine the nature of those objects.

In case of any disease like X-ray, Ultrasound, MRI. Various methods are use to diagnose the defects of our physical process. Similarly by observing the radiation of different wavelengths coming from the cosmic object to determine. What material is in the object and what kind of process is going on. Astronomers try to. Just as the use of X-rays opened a new horizon in medicine, the observation of radiation of wavelengths other than visible light brought about a revolutionary change in astronomy in the second half of the twentieth century.

But one problem is that no electromagnetic waves can reach us through the Earth’s atmosphere. Without visible light and radio waves. I call it ‘difficult’, but only in the context of astronomical research. If our atmosphere did not block strong radiation like ultraviolet, X-rays, gamma-rays, etc., then life would not exist on earth. Is that the way?


Scientists understand that this requires sending the telescope far above the surface. Where the density of the atmosphere is very low. From there, the concept of a space telescope was born. At first, experiments are carried out by sending the telescope to a great height for a short time. By means of rockets or balloons. The telescope was then sent into orbit around the Earth with the help of artificial satellites for long-term uninterrupted observation. For the last three or four decades, various cosmic telescopes have been trying to unravel. The mysteries of the universe by orbiting the earth in a specific orbit.

What does an astrostat do?

Let’s come back to the words of Astrosat. Astrosat is the first space observatory build in India. In 2004, ISRO finalized the decision to build the Astrosat. In addition to ISRO, many astronomical research centers in the country and a number of foreign companies are responsible for the manufacture of various astronomical telescopes and their components.

The Astrosat has five separate telescopes: UVIT, SXT, LexPC, CZTI, and SSM. A special feature of the Astrosat is that these telescopes can be use to observe a wide range of electromagnetic spectra, from ultraviolet to low-energy and high-energy X-rays. This is not possible with any other telescope in the world. The astrosate observes shorter wavelengths, or more powerful radiation, than visible light.


This type of radiation comes from sources in the universe where various high-powered physical processes take place. For example, the parts of the galaxy where new stars, supernova explosions, and a variety of special stars are formed, such as white dwarfs and neutron stars, whose gravitational force is about 10,000 to 100 million times greater than that of the Sun, respectively.


And the most well-known source of high-energy cosmic radiation is the black hole, whose gravitational force is so great that even light cannot escape from it. Due to the strong attraction of white dwarfs, neutron stars or black holes, gaseous matter flows towards them rapidly from any ordinary star very close to them and becomes very hot. Ultraviolet and X-ray waves are radiated from this heated gaseous stream.

Over the past five years, observations by astronomers have uncovered a wealth of information about various cosmic objects and processes. Astrosat’s Uvit telescope has detected ultraviolet rays from a galaxy about 9.3 billion light-years away. It provides important information about how stars, galaxies, etc. were formed at the very beginning of the history of the universe.

Exactly this type of observation has not been make possible by any other telescope before. When the star explodes towards the end of the life of many heavier stars from the Sun, forming a black hole, a large amount of low-energy gamma-rays are emitted within a few seconds. This is the first time that AstroSat’s CZTI telescope has been able to accurately detect the polarization of that gamma-ray and its change over time.


From this, a lot of unknown information can be known about what kind of physical process takes place in the last part of the life of a star. Earlier, Astrosat had similarly detected the polarization of gamma-rays and found new information about the physical processes inside the Crab pulsar. This observation has left theorists quite concerned and this is where Astrosat’s success lies.

Because, when theoretical thinking has to be sort out in order to find an explanation for new observations. new horizons open up in research. Using the Uvit telescope, the ultraviolet radiation of our neighboring galaxy. Andromeda is being survey in a systematic way .which shows the rate at which new stars are forming in the central region of that galaxy. The SXT and LexPC telescopes have revealed a lot of new information about neutron stars scattered to us . other nearby galaxies, massive black holes near the Sun, and black holes millions of times heavier than the Sun at the center of distant galaxies and the flow of heated gas around them.

Astrosat satellite
photo credit: isro

As Astrosat has made some unexpected discoveries, some of the expected microscopic observations have yet to be made. According to the initial design of the instrument, the planned lifespan of the Astrosat was five years. Although some parts have been partially crippled, each telescope is still operational. ISRO has decided to maintain the Astrosat’s operation. However, the importance of astrosat is not limite to performance skills. Some more Indian space-telescopes are set to be launch into orbit in the next few years. Astrosat has the courage to take them forward and to help build better space-telescopes.

photo credit : isro

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