How first extreme-UV light appeared

  • Scientists have uncovered an important clue on how the dark ages of the Universe ended and how the first extreme-UV light appeared.
  • India’s first multi-wavelength satellite, AstroSat, has detected extreme-UV (EUV) light from a galaxy, called AUDFs01, 9.3 billion light-years away from Earth. 
  • At the time, our universe was forming stars at its peak rate. 
  • Such EUV radiation has enough energy to ionize a hydrogen atom by liberating its electron from the nucleus’s influence.
  • The EUV photons emitted by galaxies like AUDFs01 could play a crucial role in reionizing the early universe soon after the Cosmic Dark Age and emitting the first light.
  • A collaboration of researchers from different countries under the project CEFIPRA funded by 
  • Indo-French Centre for the Promotion of Advanced Research (CEFIPRA) a bilateral organization set up by the Department of Science & Technology, Government of India and the Ministry for Europe and Foreign Affairs, Government of France delved into how galaxies like AUDFs01 grow their stellar mass when the first stars and galaxies became visible.
  • The team estimated the recent star-formation rate and mass of the gas reservoir in the galaxy. 
  • Star formation rate provides a quantitative measure of the stellar mass growth in galaxies. 
  • The typical star formation rate (or gas consumption rate) in those first galaxies is not known. 
  • By studying galaxies like AUDFs01 and many more, we could get an idea of how star formation rate, gas consumption rate, and growth of stellar mass in those primitive galaxies.
  • The multi-wavelength satellite AstroSat, which was launched on September 28, 2015, by the Indian Space Research Organisation (ISRO) has five unique X-ray and ultraviolet telescopes working in tandem and has onboard the UltraViolet Imaging Telescope (UVIT).
  • AUDFs01 is the first example of a leaking galaxy with clumpy morphology. 
  • This galaxy has four clumps and, perhaps, typical of star-forming galaxies in this redshift range.