Astronomers in Poland have identified a nearby exoplanet with a mass exceeding 11 times that of Jupiter, placing it among the most massive known planets.
Classified as a cold super-Jupiter, this exoplanet is significantly larger and colder than Jupiter, which serves as the benchmark for the largest planets. Details about this massive exoplanet and its host star system were outlined in a paper published recently in Astronomy & Astrophysics.
Located just over 300 light-years from Earth in the Great Bear constellation, the exoplanet is part of a multi-planet system. The host star, HD 118203, is approximately 20 percent more massive and twice as large as the Sun, and is older than our star. Another planet in the system, a hot Jupiter that is twice the size of Earth, was previously detected by the Transiting Exoplanet Survey Satellite (TESS) in 2005.
"Doppler observations suggested the existence of an additional planet," said Andrzej Niedzielski, an astronomer at Nicolaus Copernicus University in Poland, in a university release. "Thus, we included this system in our observational programs."
With the help of TESS data and measurements from the 3.6-meter Telescopio Nazionale Galileo and the approximately 9-meter Hobby-Eberly Telescope in Texas, the research team discovered another object orbiting the star. Although the planet itself is not visible due to the star’s brightness, its presence was inferred from radial velocity data, which showed slight variations in the star’s brightness over time.
An interesting aspect of this system is the hot Jupiter, discovered in 2005, which has an orbit of just over six days. In contrast, the newly identified cold super-Jupiter takes about 14 years to complete one orbit around its star.
Despite its notable size, this exoplanet is not the largest known to scientists. The largest recorded planet is TrES-4b, located about 1,430 light-years away in the constellation Hercules, with a diameter of 142,915 miles (230,000 kilometers) compared to Jupiter’s diameter of 88,670 miles (142,700 kilometers). However, TrES-4b is less massive than Jupiter, making the newly discovered exoplanet denser.
While the distinction between the most massive exoplanet and the least massive brown dwarf often blurs, the cold super-Jupiter, at around 11 Jupiter masses, is comparable to Beta Pictoris b, which is approximately 12 times Jupiter’s mass and located 63 light-years from Earth.