A series of new studies shows how quickly the amount of gas and dust decreases in protoplanetary disks. It turns out that the former disappears faster than the latter, but overall the dynamics are quite complex and this greatly influences which planets form in a given star system.
Protoplanetary disk
For the first time, scientists have been able to study in detail how the amount of gas and dust in protoplanetary disks changes over time. The Atacama Large Millimeter/submillimeter Array (ALMA) helped them achieve this, and the results are presented in 12 scientific publications.
Protoplanetary disks are dense clouds of dust and gas that spin fast in one plane around young stars. It’s where particles collide, stick together, and eventually form planets. Scientists believe that the shape of the disks influences the type of bodies that form within them: whether they will be similar to Earth or gas giants.
Protoplanetary disks exist around stars for several million years before they completely dissipate, leaving only planets behind. And scientists are very interested in how the dust and gas content changes in them over time.
As for gas, this had been studied using ALMA even earlier, but gas is much more difficult to study. Therefore, scientists had to conduct much more research using a radio telescope, but they still determined what was happening to it in the protoplanetary disk.
Gas disappearance
During the study, scientists used ALMA to examine 30 protoplanetary disks. They are located in several star-forming regions of different ages: Ophiuchus (the youngest), Lupus (1-3 million years old), and Upper Scorpio (the oldest). Thanks to this, they were able to track the entire process of protoplanetary disk evolution.
The main conclusion drawn by scientists is that in the early stages, gas disappears from the systems much faster than dust. If at the age of about 1 million years its total mass is equal to several Jupiters, then at about 3 million years it is less than 1 Jupiter mass. However, this process then stops, and systems that are 5-6 million years old contain less gas, but still more than previously expected.
All this has implications for the theory of protoplanetary system formation. Because it turns out that gas giants like Jupiter have a very short time to form — literally a few million years. This means that their formation should be completed earlier than that of rocky planets.
According to phys.org
