Oral Presentation

Can planetesimals form dry?

Author(s): Hauyu Baobab Liu (ASIAA)

Presenter: Hauyu Baobab Liu (ASIAA)

The surface stickiness of dust grains dictates the efficiency for the circumstellar dust to coagulate to form millimeter-sized grains or larger bodies, which are ingredients to form terrestrial planets. The laboratory experiments carried out after 2018 indicated that the dry silicate or refractory organic dust in the high-temperature (e.g., >150 K) regions may be stickier than the water-ice coated dust. However, the composition and morphology of the circumstellar dust are not necessarily similar to the laboratory sample. To understand the dust stickiness, it is essential to constrain the dust maximum grain sizes in the protoplanetary disk. Based on extensive JVLA and ALMA observations on the accretion-outburst YSO, FU Ori, at 8-345 GHz, and the complementary Herschel, Spitzer, and VLTI/GRAVITY spectra, we demonstrate that the >150 K region in the FU Ori hot inner disk is indeed prone to form millimeter-sized dust. On the contrary, the maximum grain sizes in the <150 K region remain smaller than 200 microns. Our measurement is working in concert with modern laboratory experiments. Forming grown dust in the high-temperature regions may be a key to explaining why the Earth, Mars, and objects in the main asteroid belt are deficient in water and carbon. These results may also have implications for the detection statistics in the searches of exoplanets that were based on direct-imaging observations on the relatively low-temperature and spatially extended areas.