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Astronomers have discovered a giant exoplanet in the constellation Ursa Major. The newly identified planet has been dubbed a “super-Jupiter” because it has a mass many times that
Astronomers have discovered a giant exoplanet in the constellation Ursa Major. The newly identified planet has been dubbed a “super-Jupiter” because it has a mass many times that of the gas giant Jupiter. The discovery was made by experts from the NCU Institute of Astronomy in collaboration with researchers from Spain and the United States.
The new exoplanet is extraordinary. It is 11 times larger than Jupiter, the largest planet in our solar system. According to the researchers, the planet orbits its host star in 14 years and maintains a temperature of no more than minus 100 degrees Celsius.
The giant world is six astronomical units (AU) away. To put that into perspective, an AU is the average distance between Earth and the Sun — about 150 million kilometers.
The head of the NCU research team, Hracjan Macievski, noted that although the team could not see the planet itself, they could see the star it orbited.
“The physical parameters of the star are similar to the Sun. The data show that it is 20 percent larger than the Sun and twice as massive,” Maceevsky said. “Interestingly, it has already completed the evolutionary stage that the Sun is in now; it has five billion years behind it. So we can estimate that this is also the age of the entire planetary system.”
Maceejewski explained that the planet is located in the northern part of the sky, in the constellation Ursa Major, and has the name HD 118203, because it was first entered under this number in Henry Draper’s star catalogue. “The telescope with which the observations for this catalogue were made more than a century ago is now located in our observatory in Pivnice near Toruń,” Maciejewski said.
For nearly 20 years, astronomers have known that the star HD 118203 has a fairly large planetary companion. In 2006, the first gas giant orbiting a star twice the size of Jupiter was discovered, completing its orbit in just six days.
“But the Doppler observations showed that this is not the end of the story, that there may be another planet out there. That’s why we immediately included this system in our surveillance programs,” said Andrzej Niedzelski, co-author of the study.
“Initially, we tracked the object using one of the largest optical instruments in the world, the 9-meter Hobby-Eberly Telescope in Texas, as part of the Toruń-Pennsylvania exoplanet search program conducted in collaboration with Professor Oleksandr Wolshchan.”
The encouraging initial results prompted the team to continue their observations, this time using the Italian Galileo telescope in the Canary Islands, equipped with modern instruments designed to detect planets. But eight years of research have not yet provided an answer to what kind of object has been discovered.
It took another seven years for astronomers in Toruń to gather indisputable evidence that they had indeed found a planet.
“Patience pays off,” Maceevsky said. “New observations collected in March 2023 were decisive in determining the planet’s orbital parameters. “Moreover, since the planet takes several years to orbit its star, we were able to combine our Doppler observations with existing astrometric measurements to precisely determine its mass. This allowed us to build a complete model of this planetary system and study its dynamical behavior.”
Before they could fully confirm the discovery of a super-Jupiter, the team needed to make sure there were no other large planets in the system. This task was undertaken by astronomy student Julia Serzputovska.
“I analyzed photometric observations from the Transiting Exoplanet Survey Satellite, showing that there are no other planets larger than twice the mass of Earth around HD 118203 and therefore it is not large enough to study the dynamics of the system,” he said.
Krzysztof Gozdziewski, who has conducted detailed numerical studies of the system’s dynamics, noted that the HD 118203 system contains a hierarchical planetary system. “This is a special configuration where one planet forms a close pair with its star, and the second planet orbits the pair in such a wide orbit that it forms another pair, so to speak, with the first one,” Goziewski explained.
Both planets are large and move in elliptical orbits, but despite their gravitational interactions the system remains stable for millions of years.
“We showed that this is due to effects from the theory of general relativity. If there were no such effects, the planets would behave like nerve springs, constantly changing the shape of their orbits and their orientation in space,” Godziewski added.
The discovery of this hierarchical planetary system adds a new piece to the puzzle of how planetary systems, especially those with large planets, form and evolve. Such systems allow astronomers to improve their understanding of planetary dynamics.
“It’s an interesting question about the ways in which such planetary configurations could develop,” Maceevsky said.
“Even though they may be quite ‘exotic’ from our perspective as Solar System inhabitants, studying systems with large gas planets seems important for our ability to get to know our closest astronomical backyard.”
The team is still observing and analyzing data, Niedzelski said, because there is a chance for more planetary discoveries. “It’s good that we can involve students and PhD students in this interesting and important research.” The study was published in the journal Astronomy and Astrophysics.
Source: Port Altele
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