University of Heidelberg

Talk Details

Monday, July 21, 2014 - 11:00am

Joanna Drazkowska (ZAH/ITA):

"Pebble-Pile Planetesimal Formation"

Abstract. There are almost 2000 known exoplanets and indirect methods indicate that every star in our Galaxy has at least one planet. Nevertheless, although the planet formation processes are ubiquitous, their details still remain a mystery. In general, planets form in disks surrounding young stars, starting from micron-sized grains that are already present in the interstellar medium. Analytical and numerical models of dust evolution aim to explain the growth of the primordial grains through 40 orders of magnitude in mass, up to more than 1000 km-sized planets. However, these growth processes encounter serious obstacles even at mm-sizes, which are known as growth and drift barriers. I will briefly review these issues and I will focus on the possibility of planetesimal formation by gravitational collapse of dense dust clumps produced by two-fluid instability, known as the streaming instability. While this is a potentially very efficient way of overcoming both growth and drift barriers, strong clumping, which can lead to planetesimal formation, requires relatively abundant population of mm- to cm-sized aggregates, known as pebbles. Considering that state-of-the-art streaming instability models do not take into account realistic size distributions, which are resulting from dust collisional evolution, I will investigate whether sufficient amount of large grains can be produced by dust aggregates sticking and what is the interplay of the coagulation and planetesimal formation in this scenario.

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