2/22/2021

Galaxies & Cosmology & Stars & Planets Seminar

Monday, February 22, 2021 - 11:00am

Zoom

Plasmas Far from Equilibrium

Speaker:

Kristopher Klein

Institution:

University of Arizona

Visitor Schedule

Host:

Rob Hargreaves

Abstract

The hot and diffuse nature of the Sun's extended atmosphere allows it to persist in non-equilibrium states for long enough that wave-particle instabilities can arise and modify the evolution of the expanding solar wind. Determining which instabilities arise, and how significant a role they play in governing the dynamics of the solar wind, has been a decades-long process involving in situ observations at a variety of radial distances. With in situ observations of thermal particle velocity distributions, including new measurements from Parker Solar Probe, we can study what wave modes are driven throughout the inner solar system. In particular, we use a numerical implementation of Nyquist's stability criterion to determine what wave modes could be driven as well as their associated growth rates and characteristic properties associated with different solar wind conditions. Understanding this energy transfer between thermal particles and electromagnetic fields will shed new light on thermodynamics in a variety of weakly collisional astrophysical systems, including solar and stellar winds, accretion disks, and the interstellar medium.

Probing exoplanet populations and their evolution with debris disk observations

Speaker2:

Elisabeth Matthews

Institution2:

University of Geneva

Visitor Schedule

Host2:

Jason Eastman

Abstract

Circumstellar debris dust is believed to be associated with extrasolar planets, and there is some observational evidence suggesting a link between giant, wide separation planets and debris dust. Of particular interest are those systems where the debris dust is sculpted, i.e., where there is some dynamical hint at the possible presence of these giant planets - for example, sharp edges to debris rings, or two-belt systems where the rings of dust enclose a gap. If we assume that the gravitational influence of one or more giant planets is responsible for forming such a gap, dynamical arguments allow us to predict the number and mass of planets we expect to find in these debris gaps. To fully understand the correlations and relationship between debris dust and planets requires both large scale surveys, and modelling of individual debris disks and planetary systems. In this talk I will describe our efforts to directly image giant planets in thermal emission, and debris disks in scattered light. I will present the results of two recent surveys using VLT/SPHERE to search for planets in dusty systems, and in systems with dust carved into two distinct belts. Highlights of these surveys include the first well resolved image of the HD129590 debris disk and the detection of two companions on the stellar/substellar boundary.

Event Status:

Active

2/22/2021

Events