Judit SZULAGYI

Judit Szulagyi

Interview

How did you discover la Fondation CFM ?

I saw the advertisement for the PhD grant on the website of the Doctoral School (Université de Nice Sophia Antipolis).

How has the Fondation helped you?

I appreciate a lot the financial support from the Fondation CFM, which allowed my doctoral studies in Nice. In addition to the scholarship for 3 years, I also receive a travel grant from the Foundation which I am using to attend conferences. The Foundation provides these grants very generously so that I should not worry about how I can survive living in such expensive place like Nice and also allow me to attend workshops, summer schools, and conferences which are essential parts of the doctoral studies.

What factors contributed to your choosing your field of study?

Around age of 14 I decided to be an astronomer, because I read a lot about the topic and I fell in love with astronomy. I have been always fascinated by the planets, how they formed, what are their characteristics in our own Solar System and beyond. I think, one of the most interesting question in today’s astronomy is how exactly planets formed. I am very lucky to work on this subject and add pieces to the puzzle, participating in the creation of theories to describe the variety of planets we see in the universe.

Thesis Summary:

Gas accretion onto Giant Planets

The planets are formed in gas-dust (so-called protoplanetary) disks around young stars. The giant planet formation in particular has two main stages. First, a solid core of about 10 Earth-masses are formed by coagulation of small bodies. Then, the gas is trapped around the core from the disk, thereby forming a thick, massive atmosphere. In this second stage the greater the mass of the planet, the greater the rate of capturing the gas. This leads to a runaway accretion of gas, which means that the total mass of the planet increases exponentially with time. This exponential accretion continues until there is gas available in the vicinity of the planet. It is well known that the planet is collecting gas along its path while orbiting around the star and this way it is opening a gap in the circumstellar disk. The width and depth of the gap scales with the mass of the planet, so the accretion of gas have to stop when the planet is massive enough to clear out its orbit. However, hydrodynamic simulations showed that the process of gas accretion stops only when the planet reaches the mass of ~5 Jupiter-mass. It is therefore expected that most giant planets have a mass of several Jupiter-masses. However, the observations of planets outside the Solar System show that most of the giant planets are as massive as the Jupiter or less, there is very few planets over 1 Jupiter-mass. The existence of planets with masses comparable to that of Saturn-mass (1/3 of the mass of Jupiter) is particularly surprising in the view of the above explained – and till now most accepted – theory. My thesis is try to solve this dichotomy between the theory and observations.

For this purpose I am using a hydrodynamic computer code to simulate the late phase of the giant planet formation, focusing on the gas accretion process. During my thesis I try to find out how the initial parameters (such as the viscosity, thermodynamical equation-of-state) influences the gas accretion process and give an estimate on the timescale of this process.