Using the Atacama Large Millimeter / Submillimeter Array (ALMA), of which the European Southern Observatory (ESO) is a partner, astronomers have for the first time obscured the presence of a disk around a planet outside our solar system. The observations will shed new light on how moons and planets form in young galaxies.
“Our work presents a clear trace of a disk in which satellites can form,” said Myriam Benisty, a researcher at the University of Grenoble, France, and at the University of Chile, who led the new study published today. in The Astrophysical Journal Letters. “Our ALMA observations were obtained with such an exquisite resolution that we could clearly identify that the disk is associated with the planet and we can limit the size for the first time,” she adds.
The disk in question, called an orbiting disk, encompasses the exoplanet PDS 70c, one of two gigantic, Jupiter-like planets orbiting a star nearly 400 light-years away. Astronomers had previously found hints of a “moon-shaped” disk around this exoplanet, but because they could not tell the disk clearly from the surrounding environment, they could not confirm the detection – until now.
In addition, Benisty and her team, with the help of ALMA, found that the disk is about the same diameter as the distance from our sun to Earth and enough mass to form a maximum of three satellites the size of the moon.
But the results are not just the key to figuring out how months come to be. “These new observations are also very important to prove planetary theories that have not been tested so far,” said Jaehan Bae, a researcher at the Earth and Planets Laboratory of the Carnegie Institution for Science, USA, and author on the study.
Planets form in dusty disks around young stars, cutting cavities as they emit material from this circumferential disk to grow. In this process, a planet can get its own orbiting planetary disk, which contributes to the growth of the planet by regulating the amount of material on it. At the same time, the gas and dust in the orbiting planet can come together in gradually larger bodies due to multiple collisions, which eventually lead to the birth of moons.
But astronomers do not yet fully understand the details of these processes. “In short, it is still unclear when, where, and how planets and moons form,” explains ESO research fellow Stefano Facchini, also involved in the study.
“More than 4,000 exoplanets have been found so far, but all were discovered in adult systems. PDS 70b and PDS 70c, which form a system reminiscent of the Jupiter-Saturn pair, are the only two exoplanets found so far that are still in the process of being formed, “explains Miriam Keppler, researcher at the Max Planck Institute for Astronomy in Germany and one of the co-authors of the study ,
“This system therefore offers us a unique opportunity to observe and study the processes of planetary and satellite formation,” adds Facchini.
PDS 70b and PDS 70c, the two planets that make up the system, were first discovered with ESO’s Very Large Telescope (VLT) in 2018 and 2019 respectively, and their unique nature means that they have been observed several times since with other telescopes and instruments ,
The latest high-resolution ALMA observations have now allowed astronomers to gain further insight into the system. In addition to confirming the detection of the planetary disk around PDS 70c and studying the size and mass, they found that PDS 70b shows no clear evidence of such a disk, indicating that it was starved of PDS 70c from dust material from his birth environment. ,
An even deeper understanding of the planetary system will be achieved with ESO’s Extremely Large Telescope (ELT), currently under construction at Cerro Armazones in the Chilean Atacama Desert. “The ELT will be the key to this research, because with its much higher resolution we can map the system in detail,” says co-author Richard Teague, a researcher at the Center for Astrophysics | Harvard & Smithsonian, United States. In particular, by using the ELT’s Mid-infrared ELT Imager and Spectrograph (METIS – https://elt.eso.org/instrument/METIS/), the team will be able to observe the gas movements around PDS 70c around a full 3D image of the system.