Wednesday Colloquium


"Disk-Planet Interactions: Formation of Mean-motion Resonances in a Gaseous Protoplanetary Disk"

Zijia Cui (University of Szczecin)

In recent decades, more than 800 multi-planetary systems with a great variety of the architectures have been discovered. The fundamental role in shaping the planetary systems during the early stages of their evolution, plays planetary migration. The newly born or still forming planets embedded in a gaseous protoplanetary disk move around their host stars in orbits modified continuously by their gravitational interactions with the material in the disk. It is expected that, when the relative migration of two planets is convergent, then the capture into a mean-motion resonance can occur. Is this expectation always met? In my presentation I will answer this question, on the basis of a full two-dimensional hydrodynamic treatment of the disk-planet interactions, accompanied, where relevant, with the analytic estimates of the effects of the density waves excited by the planets in the disk. I will focus on the systems containing the most numerous planets known till now, called super-Earths or mini-Neptunes. I will demonstrate that a system of two super-Earths can be repelled from the first-order resonance configurations due to the wave-planet interactions and I will give the conditions, which must be satisfied for that. My results provide one of the possible reasons why there are not so many planet pairs observed to be locked in the mean-motion resonances.



After June 8th summer break till end of September

"First image of the black hole shadow in the Galactic Center"

Maciej Wielgus (Max Planck Institute for Radio Astronomy, Bonn,)

There is a supermassive compact object, named Sagittarius A*, in the center of the Milky Way. We have recently obtained the highest resolution images of this object with the Event Horizon Telescope, a global network of radio telescopes operating at high frequency of 230 GHz. In this talk I will discuss the challenges related to obtaining these images, their theoretical interpretation, as well as the question of how much confidence do we have in Sagittarius A* being a Kerr black hole, following these new results.



Since June 9th - summer break till end of September