Astronomers have discovered a “hot Jupiter” exoplanet that orbits rapidly around a star located 725 light-years away.
The exoplanet, named TOI-1789b, is situated very close to the aging TOI-1789 star, at just 0.05 astronomical units (AU), which is about one-tenth the distance from the Sun to Mercury, according to the Indian Space Research Organization.
Simulation of exoplanet TOI-1789b. (Image: Sci-News)
Scientists from the Physical Research Laboratory (PRL), led by Professor Abhijit Chakraborty, spent three months monitoring TOI-1789b using the PARAS spectrograph at the Abu Observatory in Rajasthan, India, and found that the celestial body completes an orbit in just 3.2 days. In comparison, Mercury takes 88 days to orbit the Sun.
TOI-1789b is a giant gas planet similar to Jupiter, often referred to as a “hot Jupiter.” Due to its proximity to its host star, its surface temperature reaches 1,727°C and is expanding.
This explains why the planet has a radius 1.4 times that of Jupiter, even though its mass is only about 70%. This makes it one of the lowest-density planets known, at approximately 0.31 g/m³. For comparison, Jupiter has a density of 1.33 g/cm³.
The star TOI-1789, which is 1.5 times the mass of the Sun, is believed to be in the final stages of its evolutionary process. Therefore, this discovery holds significant importance.
“The discovery of a system like TOI-1789 will help us better understand the mechanisms driving the expansion of hot Jupiters, as well as provide opportunities to study the evolution of stars and the planets orbiting them”, Chakraborty shared.
The details of the research have been published in the Monthly Notices of the Royal Astronomical Society.
