Eddie Gonzales Jr. – MessageToEagle.com – Astronomers have detected the presence of a disk around a planet outside our Solar System for the first time. The observations – made with the Atacama Large Millimetre/submillimeter Array (ALMA) – will shed new light on how moons and planets form in young stellar systems.
Moons in the making: Two planets exist in the disk of the star PDS 70 (left), which is about 400 light-years away. The Jupiter-like planet PDS 70c is surrounded by a disk in which satellites can form. It is clearly visible in the close-up image (right). Researchers took the images with the Atacama Large Millimeter/submillimeter Array (ALMA). Image credit: ALMA (ESO/NAOJ/NRAO)/Benisty et al.
“Our work presents a clear detection of a disk in which satellites could be forming,” says Myriam Benisty, a researcher at the University of Grenoble, France, and at the University of Chile, who led the new research published today in The Astrophysical Journal Letters.
“Our ALMA observations were obtained at such exquisite resolution that we could clearly identify that the disk is associated with the planet and we are able to constrain its size for the first time,” she adds.
The disk in question, called a circumplanetary disk, surrounds the exoplanet PDS 70c, one of two giant, Jupiter-like planets orbiting a star nearly 400 light-years away. Astronomers had found hints of a “moon-forming” disk around this exoplanet before but, since they could not clearly tell the disk apart from its surrounding environment, they could not confirm its detection—until now.
In addition, with the help of ALMA, Benisty and her team found that the disk has about the same diameter as the distance from our Sun to the Earth and enough mass to form up to three satellites the size of the Moon.
But the results are not only key to finding out how moons arise. “These new observations are also extremely important to prove theories of planet formation that could not be tested until now,” says Jaehan Bae, a researcher from the Earth and Planets Laboratory of the Carnegie Institution for Science, U.S., and author on the study.
Planets form in dusty disks around young stars, carving out cavities as they gobble up material from this circumstellar disk to grow. In this process, a planet can acquire its own circumplanetary disk, which contributes to the growth of the planet by regulating the amount of material falling onto it. At the same time, the gas and dust in the circumplanetary disk can come together into progressively larger bodies through multiple collisions, ultimately leading 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 research.
“More than 4000 exoplanets have been found until now, but all of them were detected in mature systems. PDS 70b and PDS 70c, which form a system reminiscent of the Jupiter-Saturn pair, are the only two exoplanets detected 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 planet and satellite formation,” Facchini adds.
Written by Eddie Gonzales Jr. MessageToEagle.com Staff