GS Paper - 3 (Space Technology)

The exoplanet search and study group at the Ahmedabad-based Physical Research Laboratory (PRL), has discovered a new exoplanet orbiting too close to an evolved or ageing star with a mass of 1.5 times that of the Sun and located 725 light-years away, according to Indian Space Research Organisation.


  1. This discovery was made using PRL Advanced Radial-velocity Abu-sky Search (PARAS) optical fibre-fed spectrograph, the first of its kind in India, on the 1.2-metre Telescope of PRL at its Mt. Abu Observatory.
  2. Using PARAS, which has the capability to measure the mass of an exoplanet, the exoplanet's mass is found to be 70 per cent and size about 1.4 times that of Jupiter. These measurements were carried out between December 2020 and March 2021.
  3. Further follow-up measurements were also obtained from the TCES spectrograph from Germany in April 2021, and also independent photometric observations from the PRL's 43-cm telescope at Mt. Abu.
  4. The star is known as HD 82139 as per the Henry Draper catalogue and TOI 1789 as per the TESS catalogue.
  5. Hence, the planet is known as TOI 1789b or HD 82139b as per the IAU nomenclature.


  1. The detection of such a system enhances our understanding of various mechanisms responsible for inflation in hot-Jupiters and the formation and evolution of planetary systems around evolving and ageing stars.
  2. This is the second exoplanet discovered by PRL (an autonomous unit of the Department of Space) scientists using PARAS at 1.2 m Mt. Abu telescope; the first exoplanet K2-236b, a sub-Saturn size at 600 light-years away, was discovered in 2018.