Representational Image

Scientists in India working at the Physical Research Laboratory (PRL), Ahmedabad, has discovered a new planet outside our solar system (thus an Exoplanet), which is orbiting too close to an evolved or aging star with a mass of 1.5 times that of our Sun and located 725 light years away. 

The discovery of the new exoplanet has been made by PRL's Exoplanet Research and Study Group led by Professor Abhijit Chakraborty. ISRO scientists including colleagues from Europe and America, were also involved in this.

According to ISRO, this newly discovered star-planet system is a 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 (roughly one-tenth the distance between Sun and Mercury).There are less than 10 such close-in systems known among the zoo of exoplanets known so far.

The newly discovered exoplanet’s mass is found to be bigger than Jupiter, largest planet of our solar system. The exoplanet, known as TOI 1789b or HD 82139b, is 70% and size about 1.4 times that of the Jupiter.

Artistic impression of the TOI-1789 star-planet system, along with characteristics of planet
[Image ~ ISRO]

The exoplanet's close proximity to its host star makes it extremely hot with a surface temperature reaching up to 2000 K (approx. 1727 degree Celsius), and hence an inflated radius, making it one of the lowest density planets known (density of 0.31 gram per cc). Such close-in exoplanets around stars (with distance less than 0.1 AU) with masses between 0.25 to a few Jupiter mass are called "Hot-Jupiters". 

The discovery is made using PRL Advanced Radial-velocity Abu-sky Search (PARAS) optical fiber-fed spectrograph, the first of its kind in India, on the 1.2 metre Telescope of PRL at its Mt. Abu Observatory.

This is the second exoplanet discovered by PRL 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. 

Founded in 1947 by Dr. Vikram Sarabhai, the Physical Research Laboratory ( PRL ) is known as the cradle of Space Sciences in India. As a unit of Department of Space, Government of India, PRL carries out fundamental research in selected areas of Physics, Space & Atmospheric Sciences, Astronomy, Astrophysics & Solar Physics, and Planetary & Geo-Sciences.

This discovery work has been published in the refereed journal Monthly Notices of the Royal Astronomical Society, titled "Discovery of an inflated hot Jupiter around a slightly evolved star TOI-1789”, authored by Akanksha Khandelwal, Priyanka Chaturvedi, Abhijit Chakraborty, Rishikesh Sharma, Eike W Guenther, Carina M Persson, Malcolm Fridlund, Artie P Hatzes, Neelam J S S V Prasad, Massimiliano Esposito, Sireesha Chamarthi, Ashirbad Nayak, Dishendra, Steve B Howell Monthly Notices of the Royal Astronomical Society, Published: 23 October, 2021 


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