India’s AstroSat satellite detects extreme UV light from galaxy 9.3 billion light-years away from Earth


In an achievement for Indian astronomers, the Inter-University Centre for Astronomy and Astrophysics (IUCAA) on Monday informed that India’s first multi-wavelength satellite, AstroSat, has detected an extreme ultraviolet (UV) light from a galaxy which is 9.3 billion light-years away from Earth. The major breakthrough was achieved by a global team led by Pune-based IUCAA scientists, the centre said in a release.

“India’s first multi-wavelength satellite, which has five unique X-ray and ultraviolet telescopes working in tandem, AstroSat, has detected extreme-UV light from a galaxy, called AUDFs01, 9.3 billion light-years away from Earth,” the release by IUCAA said. Published on August 24 by the ‘Nature Astronomy’, the discovery was made by the international team of astronomers led by Dr Kanak Saha, associate professor of astronomy at the IUCAA, the release added.

This team comprised scientists from India, France, Switzerland, the USA, Japan and The Netherlands. Dr Saha and his team observed the galaxy, which is located in the Hubble Extreme Deep field, through AstroSat. These observations lasted for more than 28 hours in October 2016, the release stated. “But it took nearly two years since then to carefully analyse the data to ascertain that the emission is indeed from the galaxy. Since UV radiation is absorbed by Earths atmosphere, it has to be observed from space”, it said.

The release further stated that, earlier, NASAs Hubble Space Telescope (HST), a significantly larger than UVIT (UV imaging telescope), did not detect any UV emission (with energygreater than 13.6 eV) from this galaxy because it is too faint. AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVITdetector is much less than the ones on HST,” said the release quoting Dr Saha. He said that his team knew it would be an uphill task to convince the international community that UVIT has recorded extreme-UV emission from this galaxy when more powerful HST has not.

Dr Somak Raychaudhury, Director of IUCAA, as quoted by PTI, said, “This is a very important clue to how the dark ages of the universe ended and there was light in the universe. We need to know when this started, but it has been very hard to find the earliest sources of light. I am very proud that my colleagues have made such an important discovery.”


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