首页

Dust grains shine brightly in proto-planetary disks. If these grains become large enough and dense enough, they can stir the gas via the so-called streaming instability. The turbulent gas may then cluster the grains into even denser clumps, possibly triggering the formation of planetesimals. I will first describe our not-entirely-successful efforts to quantify the few key steps in this picture. However, are dust grains large enough and dense enough in real disks? I will use ALMA observations as my crutch to propose a 'small-grain hypothesis', that most grains in real disks have not grown to beyond 100-microns, possibly as a result of grain surface physics. They are thus much smaller than the favoured 'pebbles' (cm-sized) and may not concentrate strongly near the  midplane. If so, can streaming instability still operate?

BIO

Yanqin Wu is Professor of Astronomy at the University of Toronto. Originally from Guangzhou, China, she earned her Ph.D. at Caltech under Peter Goldreich and joined U of T in 2003. Yanqin works on a broad range of research topics and has done influential works on planets, stars, disks, and so on. Her recent honours include the 2026 AAS Dirk Brouwer Award, election as an International Honorary Member of the American Academy of Arts & Sciences (2024), the CAP-CRM Prize in Theoretical Physics (2023), and a Guggenheim Fellowship (2022).

Host: Wei Zhu