Ahmedabad-based PRL discovers star-planet bigger than Jupiter

The star is known as HD 82139 as per the Henry Draper catalogue and TOI 1789 as per the TESS catalogue. Hence, the planet is known as TOI 1789b or HD 82139b as per the IAU (International Astronomical Union) nomenclature.

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

“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. Using PARAS, which has the capability to measure mass of an exoplanet, the exoplanet’s mass is found to be 70% and size about 1.4 times that of Jupiter,” ISRO said in its statement.

“There are less than 10 such close-in systems known among the zoo of exoplanets known so far. Because of the close proximity of the planet to its host star, it is extremely heated with a surface temperature reaching up to 2000 K, and hence an inflated radius, making it one of the lowest density planets known (density of 0.31 gram per cc),” ISRO statement read.

This discovery was led by a team of Prof Abhijit Chakraborty, comprising his students, team members, and international collaborators from Europe and the US. While these measurements were carried out between December 2020 and March 2021, further follow-up measurements were obtained from TCES spectrograph from Germany in April 2021, and also independent photometric observations from the PRL's 43-cm telescope at Mt. Abu.

The star is known as HD 82139 as per the Henry Draper catalogue and TOI 1789 as per the TESS catalogue. Hence, the planet is known as TOI 1789b or HD 82139b as per the IAU (International Astronomical Union) nomenclature.

This newly discovered star-planet system is extraordinary, the planet orbits the host star in just 3.2 days, placing it very-very close to the star at a distance of 0.05 AU. Such close-in exoplanets around stars (with distance less than 0.1 AU) with masses between 0.25 to a few Jupiter masses are called "Hot-Jupiters", the researchers said.

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 aging stars says, researchers.

The research findings have been written by Akanksha Khandelwal, Abhijit Chakraborty, Rishikesh Sharma, Ashirbad Nayak, Dishendra and Neelam JSSV Prasad from PRL; Priyanka Chaturvedi, Eike W Guenther, Artie P Hatzes, Massimiliano Esposito and Sireesha Chamarthi, from TLS Tautenburg, Germany; Carina M Persson and Malcolm Fridlund from the Department of Space, Earth and Environment, Chalmers University of Technology, Sweden and Steve B Howell from NASA Ames Research Centre.