22 ASTROSAT
Naseer Iqbal
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From the very beginning, man has looked at the sky and wondered about the shining objects during the night. What are these shining stars, what makes them shine, where are they located and similar other questions had haunted human mind since ages. It has been said that human eye can detect ~ 2000 stars in the night sky. While most stars appeared constant in the sky, many of them appeared to change brightness. On rare occasions, suddenly a bright new star termed as ‘guest star’ or ‘Nova’ appeared in the sky. One such spectacular event was recorded by Chinese Astronomers in the year 1054 AD. It was so bright that it became visible even in the day for 23 days and then over the next 600 days it grew dimmer and dimmer and slowly faded away. Danish astronomer Tycho Brahe detected a similar new bright star in the year 1572 and German astronomer J. Kepler also recorded appearance of a bright new star in 1604.The mystery of these guest stars now known as ‘Supernovae’ was solved only several hundred years later. Invention of Optical telescope by Galileo in 1609 revolutionized astronomy as the dimension of the observable universe expanded dramatically from our Solar system and nearby stars to dimmer stars in distant reaches of the sky. As the size of the telescopes grew over next 400 years, man could observe fainter and farther objects leading to the land mark discovery of “Island Universes” (or Galaxies like our Milky Way) and expansion of the Cosmos by Edwin Hubble in 1920’s with the newly set up 100 inch aperture reflecting telescope at Mount Wilson in USA. Observations with the 200 inch Hale telescope at Mount Palomar in California (USA) unraveled mystery of peculiar star-like objects (now known as Quasars) that showed large shift in wavelength of their spectral lines towards red part of the spectrum (this is known as Red Shift) in 1963. The red shift was interpreted as arising due to high recession velocity of the radiating objects and this implied that they are at distances of several hundred million light years. Discovery of Quasars expanded the horizon of the universe that could be probed to farther and farther regions meaning earlier and earlier epochs of its evolutionary history.
With the launching of ASTROSAT funded by Indian Space Research Organization, Department of Space Govt of India, Astronomers in the Country believe that many new objects will come into real picture of observations which other way had not been observed so far owing to its multi- wavelength spectrum.
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