ISRO: Indian scientist discovers unique hot exoplanet bigger than Jupiter

Indian Space Research Organisation (ISRO) has said that Indian scientists have discovered a new exoplanet that is orbiting very close to an aging star with a mass of 1.5 times that of our Sun. This exoplanet is said to be 70% in mass and 1.4 times bigger than Jupiter. The newly found exoplanet, located 725 light-years away, has been discovered by the Exoplanet Search and Study Group at the Physical Research Laboratory (PRL), Ahmedabad that is being led by Prof. Abhijit Chakraborty.

"This newly discovered star-planet system is very unique - the planet orbits the host star in just 3.2 days, thus placing it very-very close to the star at a distance of 0.05 AU, which is the roughly one-tenth the distance between Sun and Mercury (sic)," ISRO said in a statement. Because of its close proximity of the planet to its star, it is extremely heated with a surface temperature reaching up to 2000 Kelvin, making it one of the lowest density planets known. Such exoplanets whose distance is less than 0.1 AU to its host start with masses between 0.25 to a few Jupiter masses are known as “Hot upiters”.

The new exoplanet nomenclature

The newly discovered 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 nomenclature, ISRO mentioned.

How was the new ‘Hot Jupiter’ exoplanet found?

The PRL Advanced Radial-velocity Abu-sky Search (PARAS) optical fiber-fed spectrograph, the first of its kind in India, was used on the 1.2 metre Telescope at PRL's Mt. Abu Observatory to discover the new exoplanet. The measurements for the ‘Hot Jupiter’ exoplanet were carried out between December 2020 and March 2021.

This is the second such exoplanet identified in the PRL by astronomers using PARAS at 1.2 m Mt. Abu telescope. The first discovery was K2-236b, a sub-Saturn-sized exoplanet discovered in 2018 which is around 600 light-years away. “The detection of such 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,” scientists of the project mentioned in the research paper titled "Discovery of an inflated hot Jupiter around a slightly evolved star TOI-1789" from the Monthly Notices of the Royal Astronomical Society journal.