My master thesis in 400 words: David Berardo

Gas giant planets such as Jupiter are some of the most massive types of planets known, both in our own solar system as well as systems around other stars. Being so massive they usually consume a significant fraction of proto-planetary material available to make planets, dictating how the rest of their solar system will form. Understanding their formation process is thus a key step in understanding how all planets form.

To do this requires both a model of planet formation as well as data to compare the model to. Direct imaging is a planet detection method in which light from a planet is observed directly, providing us with information about how bright the planet is. Since a planet will cool and get dimmer over time, if the planet’s age is known then we can ‘turn back the clock’ and determine how bright the planet was when it formed. From here we can use a formation model to compare this brightness to the formation mechanism of the planet.

The goal of my thesis was to simulate the formation of gas giant planets, in an attempt to connect the brightness and age of an observed planet to the way it formed. By simulating the formation of a planet and then allowing it to evolve to its current day conditions, I was able to construct the entire history of a planet from birth to old age. This process was done using the versatile MESA stellar evolution code, which allowed me to simulate the formation of hundreds of planets.

The specific model I studied is known as core accretion, in which the planet starts with a rocky core which then accumulates a gaseous envelope over time. There are many parameters to be tuned in this model such as the initial mass of the rocky core, the rate at which gas is added to the planet, the temperature and pressure of the gas etc. It is difficult in practice to directly measure these quantities, since that would require observing a planet that is still forming. Instead, I allowed these values to change and observed how they affected the properties of the planet that formed. This allowed me to answer questions such as how the rate of gas accretion affects the final brightness of the planet, providing a way to map quantities we can actually observe to conditions present during the planets formation.