Scientists have captured an unambiguous image of a lunar disk around an exoplanet, the first time such a thing has been photographed outside our own solar system.
Using the Atacama Large Millimeter / submillimeter Array (ALMA), astronomers focused on a still-forming solar system 400 light years away after previous observations of the system determined that a pair of gas giants in the system - similar to our system's Jupiter-Saturn pairing - was still forming.
The new image taken with ALMA is the clearest yet of the system's circumstellar accretion disk and was sharp enough to detect the circumplanetary disk around PDS 70c - so sharp in fact that astronomers are able to determine its diameter and mass.
"Our work presents a clear detection of a disk in which satellites could form ", says Myriam Benisty , researcher at the University of Grenoble, France, and at the University of Chile, who led the research published this week in Letters from the Astrophysical Journal .
“Our ALMA observations were obtained at such exquisite resolution that we were able to clearly identify that the disk is associated with the planet and we are able to constrain its size to the first time. "
Despite the comparison with Jupiter and Saturn, the size of the lunar disk around PDS 70c is enormous,with a diameter comparable to the distance between the Earth and the Sun, or about 500 times larger than the rings of Saturn. The mass of the accretion disk is sufficient to create up to three Moon-sized satellites. Image 1 of 3 (Image credit: ESO) Image 2 of 3
(Image credit: ESO) Image 3 of 3
(Image credit: ESO)
(Image credit: ESO)
Analysis: observing the formation of moons in real time is a big problem
What makes This discovery so important to astronomers is that despite the identification of over 4,000 exoplanets over the past fifteen years, these have all been found in mature systems where the formation of planets was primarily complete and any smaller ring system like those around Saturn would be virtually impossible to detect with current technology.
This means that everything we know - or think we know, to be more precise - on the formation of the moon has been largely based on what we have seen in our own solar system or through modeling, and both of these have a bias.
When all you have vu is your own planetary neighborhood, it 's easy to project that into the universe at large.speculated that gas giants existed on the outskirts of solar systems, the interior regions harboring small rocky planets.
This is not what scientists found when they began to study exoplanets for the first time, however. Instead, they found that hot Jupiters - large gas giants comparable in size to or larger than our Jupiter - are often found surprisingly close to their host star with orbital periods measuring in just a few days.
Something very similar could be the case with the formation of the moon, where direct observation can upset many or even most of our assumptions about how natural satellites end up orbiting their host planets.
Additionally, this discovery could also lose light on planetary formation as well. "These new observations are also extremely importants to prove theories of planetary formation which have not yet been tested, "Jaehan Bae, researcher at the Earth and Planets Laboratory at the Carnegie Institution for Science, USA, a co-author of the study said.