Free Astronomy Magazine September-October 2025

33 ASTRO PUBLISHING lution imaging with sparse model- ing. In radio astronomy, images are commonly restored based on a spe- cific assumption to compensate for missing observation data. The imag- ing method employed this time re- constructs based on a more accurate assumption than the conventional approach, producing higher-resolu- tion images even though the same observation data is used. PRIISM (Python module for Radio Interfer- ometry Imaging with Sparse Model- ing), the public software developed by a Japanese team was used in this study. The research team utilized this new imaging technique on ALMA archival data, targeting 78 disks in the Ophiuchus star-forming region, located 460 light years from the Solar System. As a result, more than half of the images produced in this study achieved a resolution over three times higher than that of the conventional method, which is com- parable to that of the DSHARP and eDisk projects. Moreover, the total number of samples in this study is nearly four times larger than that of the previous two projects, signifi- cantly improving the robustness of our statistical analysis. Among the analyzed 78 disks, 27 disks were re- vealed to have ring or spiral struc- tures, 15 of which were identified for the first time in this study. The team combined the Ophiuchus sam- ple with those of the eDisk project to conduct a statistical analysis. As a result, they found that the charac- teristic disk substructures emerge in disks with radii larger than 30 astro- nomical units (au) during the early stage of star formation, just a few hundred thousand years after a star was born. This suggests that planets begin to form at a much earlier stage than previously believed, when the disk still possesses abun- dant gas and dust. In other words, planets grow together with their very young host stars. Ayumu Shoshi says, “These findings, bridging the gap between the eDisk and DSHARP projects, were enabled by the inno- vative imaging that allows for both achieving high resolution and a large number of samples. While these findings only pertain to the disks in the constellation Ophiuchus, future studies of other star-forming regions will reveal whether this ten- dency is universal.” !