Free Astronomy Magazine September-October 2023

SEPTEMBER-OCTOBER 2023 I mages of disks around 19 protostars, including four binary systems observed with the ALMA. For one binary system, disks around the primary and second- ary are presented independently (2 nd line rightmost and 3 rd line leftmost). Disks are presented in the order of their evolutionary sequence (the one in the upper- left corner is the youngest while the one at the lower-right corner is the oldest). The two oldest disks show faint ring-gap structures. A scale bar of 20 au (1 au corresponds to the distance between the Earth and the Sun, which is 150 million kilometer) is shown for each disk image. [ALMA (ESO/NAOJ/NRAO), N. Ohashi et al.] tostars. Moreover, the ring structures are less distinct than those seen in the protoplanetary disks. It was also found that the dust (building blocks of planets) in many disks, is not set- tled in the disk midplane. Rather the dust is aloft, above the disk midplane, making the disks ap- pear thick in the vertical direction. In more-evolved disks, in contrast, the dust settles down in the midplane thereby making them appear much thinner. “We did not expect to see such clear differences between disks around protostars and more-evolved disks,” says Ohashi. John Tobin, a Co- PI of the program at the National Radio Astronomical Observatory (USA) adds “Our results suggest that disks around protostars are not fully ready for planet formation. We be- lieve that the actual formation of the planetary system progresses rap- idly in the 100,000 years to 1,000,000 years after star formation begins.” Jes Jørgensen, the other Co-PI of the program at the Niels Bohr Institute of University of Copenhagen (Den- mark) also mentions the importance of international cooperation in plan- ning and implementing such a large- scale program. “There are 37 re- searchers from 15 research institutes participating in the international re- search group that promoted this re- search. In addition, about half of them are graduate students or young researchers who have recently ob- tained their Ph.D. This research gives many young researchers the oppor- tunity to participate in large-scale in- ternational programs, and it can be said that this program plays a major role in nurturing future research and collaboration.” !