Context: The discovery was made by a team of astronomers led by Dr Kanak Saha from the Inter-University Centre for Astronomy and Astrophysics (IUCAA) Pune.
Key Points

• The galaxy, called AUDFs01, is 9.3 billion light-years away from Earth.
• The galaxy, one of the earliest, is located in the Extreme Deep field.
• Even though the observation was made in 2016, it took the scientists almost two years to analyse the data and ascertain that the emission was indeed from a galaxy.
• The scientists were able to discover the galaxy by detecting extreme UV radiation emanating from the galaxy.
• The discovery was made by the Indian space observatory AstroSat.
• It is remarkable that such faint UV radiation has been detected because usually, such low energy photons usually get absorbed on the way or by the earth’s atmosphere.
• Even the Hubble Space Telescope (HST) of NASA could not detect this probably due to noise.
• India’s AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVIT detector is much less than in the HST.
• The discovery has been reported in the leading international journal “Nature Astronomy” published from Britain.

About AstroSat

• AstroSat is India’s first space observatory.
• It is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical and UV spectral bands simultaneously.
• It enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
• AstroSat with a lift-off mass of 1515 kg was launched in 2015 into a 650 km orbit inclined at an angle of 6 degrees to the equator by PSLV-C30 from Satish Dhawan Space Centre, Sriharikota. The minimum useful life of the AstroSat mission is expected to be 5 years.
• The satellite is managed by the spacecraft control centre at Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC), Bengaluru.

Objectives of the AstroSat mission

• To understand high energy processes in binary star systems containing neutron stars and black holes.
• Estimate magnetic fields of neutron stars.
• Study star birth regions and high energy processes in star systems lying beyond our galaxy.
• Detect new briefly bright X-ray sources in the sky.
• Perform a limited deep field survey of the Universe in the Ultraviolet region.

About Hubble eXtreme Deep Field (XDF) and Hubble Ultra Deep Field (HUDF)

• The galaxy was observed in the sky using the Hubble eXtreme Deep Field (XDF) which sits in the centre of the Hubble Ultra Deep Field (HUDF).
• The HUDF is a small area in the constellation of Fornax which was created using Hubble Space Telescope data from 2003 and 2004.
• The HUDF contains thousands of galaxies and has become the deepest image in the universe ever taken.
• The XDF has about 5,500 galaxies which also includes those which go back about 13.2 billion years in time which is nearly as old as the universe – which is 13.7 billion years old.
• The youngest galaxy in the XDF arrived in existence around 450 million years after the Big Bang.