Is our solar system similar to other systems? What do other systems look like? Many other systems have hot Jupiters, massive gas giants that are very close to their stars. Our Solar System is the outlier, is that normal?
One way to address these questions is to study the disks around young stars to see how they evolve. The only way to get an answer is to study a large sample of these systems. A group of astronomer did a survey of 873 disks.
A new study into planet-forming disks has mass as the critical piece. The mass of the disk determines the amount of matter available to planets. Calculating the total mass of planets around young stars is a step closer to understanding solar system architecture.
The survey is about the cloud-level demographic of 873 disks.
We didn't know which properties dominated the evolution of planet-forming disks around young stars.
The mass of planets that might form from a disk is also told by the dust mass. Astronomers could use the disk's age to tell them what planets have already formed.
The factors that affect disk mass vary from disk to disk. Mass can be affected by things like stellar wind and irradiation from nearby stars. How were the effects isolated in such a large sample?
They focused on a region of disks called the Orion A cloud, which is part of the OMC. The OMCC is located about 1350 light-years away, and is home to the well-studied Orion Nebula.
A scientist at the University of Vienna is a co-author of the study.
All disks are in the same cloud, so this is a good sample. They all have the same history, and their chemistry is uniform. The team rejected any disks in the area because the ONC has some massive stars that could affect other disks.
It was difficult to measure the mass of these disks. The team used the ALMA to observe the dust. The young disks were observed at a 1.2 millimeter wavelength. The star is dim at that wavelength, which helps eliminate the effect of the star in each disk. The team measured only dust available to form new planets, since the observations were made at 1.2mm.
The researchers faced one hurdle, but another was the data.
A lot of data is created by a survey of almost 900 disks, and all that data has to be processed before it has any meaning. It would have taken six months to process all that data if the team had used existing methods. They developed their own method to handle the data. The processing speed was improved by a factor of 900 thanks to the new approach.
The researchers found that the majority of the disks held less than 2 Earth masses of dust. Only 20 of the disks held enough dust to cover 100 or more Earths. The sub-samples were large enough to yield statistically meaningful results thanks to the hundreds of disks.
There were some variability in the disk dust mass, but it was not significant. The authors say that the age effect can account for the variations. The differences between these clusters, which are located far from each other on the sky, are small and not significant relative to each other.
It is expected that the dust mass will decrease as disks age. What was once dust became planets. Dust loss is contributed to by other effects. Dust can migrate towards the disk center, and irradiation from the host star can evaporate the dust. The correlation between age and dust loss is strengthened by this study.
Can the results from this study be applied to other populations? The authors compared their results to nearby star-forming regions with young disks. Most of them fit with the age-related mass loss seen in Orion A. They seem to be evolving in the same way.
The researchers want to do more work. They are going to look at the effect smaller stars have on a small scale. They avoided the effect that ONC stars have on neighbours. Smaller background stars might explain some of the small variations in the age-mass correlation.
The age of the star and its disk, the chemical properties, and the dynamics of the parent cloud all combine with mass to paint a clearer picture of the solar system that arises from the disk. Astronomers are not able to predict what type of planets will form in any given Solar System. It is remarkable that the correlation between disk age and disk mass is strong across large structures.
The authors conclude that the remarkably homogeneous properties of disk samples of the same age are a surprising finding. For the first time, the large sample of the SODA allows us to see the effects of age and clustering in a single star-forming region.