APEX this week: The long and winding road of planet formation, with Dr Mor Rozner
14 March 2025, 1:00 pm–2:00 pm

This week at APEX we are delighted to welcome Dr Mor Rozner, a Research Fellow at Gonville & Caius college, University of Cambridge, a member of the Institute for Advanced Studies, Princeton, and a Rothschild fellow. This will be a hybrid event, held at UCL and online.
This event is free.
Event Information
Open to
- All
Availability
- Yes
Cost
- Free
Organiser
-
Dr Andrew Rushby / Dr Joanna Fabbrijoanna.fabbri@ucl.ac.uk
Location
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G22 LTNorth West Wing, UCLGower StreetLondonWC1E 6BTUnited Kingdom
Our Astrobiology and Planetary Exploration (APEX) seminar this Friday 14th March at 13:00 GMT, features the following talk:
- Mor Rozner (Cambridge) - The long and winding road of planet formation: from dust grains to hot Jupiters
An abstract for Mor's talk can be found below.
Please note the day and location for APEX this term: Fridays at lunchtime, 1-2 pm GMT, in the G22 Lecture Theatre on the ground floor of the UCL North West Wing building.
A hybrid (in-person and online) format will continue this term but, of course, we warmly encourage in-person attendance to support our visiting speakers.
Details of the forthcoming APEX programme can be found at the link below. The latest information will be advertised in advance of each meeting. If you are not on our regular mailing lists and are interested in attending these seminars, please contact joanna.fabbri AT ucl.ac.uk.
Talk abstract
The long and winding road of planet formation: from dust grains to hot Jupiters
Planet formation is a long and complicated process, spanning over a wide range of scales and processes -- from dust grains to full-scale planets, unfolding complex interplay of gravitational, hydrodynamic, and thermodynamic phenomena. In this talk, I will discuss several aspects of this process, if time allows. Planet formation requires significant amounts of gas. The role played by gas changes from one stage to another, but is essential for all of them until the disk dispersal. Inspired by Kennicutt Schmidt, which connects the gas surface density and star formation rate, we derive a correlation between the planet formation rate (PFR) and the gas surface density, i.e. PFR ∝ Σ_g^n, and examine the dependence of this quantity on the gas surface density of the protoplanetary disk in which they formed. This relation serves as an analog for the well-established Kennicutt-Schmidt law for star-forming galaxies, with proper modifications, as star formation differs significantly from planet formation. We study the different planet formation mechanisms and the density dependence in each one of them, to finally formulate simple powerlaw relations.
Then I'll focus on several specific stages of planet formation. Aeolian erosion is a destructive process that can erode small-size planetary objects through their interaction with a gaseous environment, it operates in a wide range of environments and under various conditions. Aeolian erosion has been extensively explored in the context of geophysics in terrestrial planets. Here we show that aeolian erosion of cobbles, boulders, and small planetesimals in protoplanetary discs can constitute a significant barrier for the early stages of planet formation. We discuss the connection to other processes in planet formation such as streaming instability, and possible implications for white dwarf disks.
I will then discuss the dynamics of full-scale planets. Eccentric tidal migration of hot and warm Jupiters could be enhanced when we consider initially inflated gas giants. Since all the gas giants are formed inflated by the end of core accretion, this phenomenon should be robust and shape the population of hot & warm Jupiters.
If time allows, I will discuss also the formation of Pluto-Charon from an initially wide binary.
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