Experiments on granular materials and planet formation

by Prof. Nicolas Mujica (University of Chilie)

Monday 31 Jan 2022, 15:45 → 17:45 Europe/Stockholm

zoom link : https://stockholmuniversity.zoom.us/j/622224375

 

Abstract:

Despite the abundant evidence of the existence of terrestrial planets, there is no agreement on the physical mechanisms and paths that allow their formation. Starting from 1 μm particles—dust that orbits in accretion disks, the so-called protoplanetary disks (PPD)—it is necessary to reach rocky objects with a diameter of 1 km so that gravity can act accreting more material; these objects are called planetesimals. There are several mechanisms that allow the growth of granular lumps but also others that slow down their evolution, such as bouncing, impact fragmentation, erosion and, finally, the possibility of falling to the central star induced by loss of angular momentum due to friction with the disk gas. This leads to the so-called meter barrier: theoretically, massive objects larger than this scale should not exist, which is in open contradiction to what has been observed (we are actually standing on a rocky planet).

In this talk, I will present the first experimental results of the Experimental Astrophysical Research into Terrestrial growtH (EARTH) project, where we propose to investigate the formation of planetesimals in protoplanetary disks from the point of view of granular physics. In particular, we want to elucidate the role of tribocharge between granular particles, which consists of the exchange of charges between particles (surfaces) in contact, which until now has been rather ignored. Is this the missing ingredient to bridge the gap at the meter barrier?