Indian scientists from the Ahmedabad-based Physical Research Laboratory (PRL) have recently discovered an exoplanet, named HD82139b, which is 1.4 times bigger than Jupiter, has a mass of 1.5 times of Sun, and located 725 light-years away from the Earth. Exoplanets are planets that orbit around other stars and are found outside the solar system. All planets in the solar system orbit around the sun. The discovery team comprised students and international collaborators from the US and Europe and was led by Professor Abhijit Chakroborty. This happens to be the second exoplanet discovery—the first being K2-236b, a sub-Saturn size, at 600 light-years away, was discovered in 2018.
The exoplanet was added in the Henry Draper catalogue consisting of spectroscopic classification for 2,25,300 stars. It is known as TOI 1789b, as per the (The Transiting Exoplanet Survey Satellite) (TESS) input catalogue while as per the International Astronomical Union nomenclature, it is HD82139b. TESS input catalogue is a compiled catalogue of stellar parameters for every optically persistent and stationary object in the sky.
The discovery was made using PRL’s Advanced Radial-velocity Abu-sky Search (PARAS) optical fibre-fed spectrograph. This is a first of its kind optical fibre-fed spectrograph on the laboratory’s telescope at Mt. Abu Observatory in Rajasthan, India.
This discovery was published in the refereed journal ‘Monthly Notices of the Royal Astronomical Society’ and is titled Discovery of an inflated Hot Jupiter around a slightly evolved star TOI-1789.
Some Features
The measurements related to the exoplanet were carried out during December 2020 and March 2021. Further, follow-up measurements using TCES spectrograph, in Germany, were carried out during April 2021, which showed that it was orbiting unusually close to a star, completing one orbit in just 3.2 Earth days. It is roughly one-tenth the distance between Sun and Mercury.
The observations revealed that its mass is 70 per cent, and size about 1.4 times bigger than Jupiter. There are less than 10 such close-in systems known among the zoo of exoplanets.
Due to its closeness to its host star, the planet is intensely hot, with a surface temperature of up to 2,000 Kelvin (1726.85 °C). It also has an inflated radius with a density of 0.31 gram per cc, making it one of the lowest density planets. Such extreme proximity exoplanets around the host stars with masses ranging from 0.25 to a few Jupiter masses are referred to as ‘Hot-Jupiters’.
Significance of the Exoplanet According to the astronomers, it is one of the few nearby evolved stars with a close-in planet. This discovery would contribute to our understanding of mechanisms responsible for inflation in ‘Hot Jupiters’. It would also provide an opportunity to understand the evolution of planets around stars, leaving the main sequence branch.
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