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 a distance of just 0.05 astronomical units (AU), which is equivalent to 1/10 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. They found that the celestial body completes one orbit in just 3.2 days. In contrast, Mercury takes 88 days to orbit the Sun.
TOI-1789b is a gas giant similar to Jupiter, often referred to as a “hot Jupiter.” Due to its proximity to its host star, it has a surface temperature of 1,727°C and is undergoing expansion.
This is why the planet has a radius 1.4 times that of Jupiter, despite having only 70% of Jupiter’s mass. This makes it one of the lowest-density planets ever known, at approximately 0.31 g/m³. For comparison, Jupiter has a density of 1.33 g/cm³.
The TOI-1789 star, which is 1.5 times the mass of the Sun, is believed to be in the final stages of its evolutionary process. This discovery is therefore particularly significant.
“The discovery of a system like TOI-1789 will help us better understand the mechanisms behind hot Jupiters, as well as provide an opportunity to study the evolutionary processes of stars and the planets that orbit them,” Chakraborty shared.
The details of the research were published in the Monthly Notices of the Royal Astronomical Society.
