420 Davey Lab
University Park, PA 16802
Email: danielc@psu.edu

Research: Formation and evolution of exoplanet systems

I am a NASA Postdoctoral Fellow at the Center for Exoplanets and Habitable Worlds at the Pennsylvania State University. My research interests include the formation and evolution of planetary systems, and the origin of volatiles (water and atmosphere) in super-Earths, and exoplanet habitability. Super-Earths are a type of exoplanet with a size between that of Earth and Neptune. While there are no super-Earths in the solar system, they are the most commonly observed type of planet in the Galaxy. Approximately half of all stars have super-Earths with short orbital periods. Therefore, it is important that we understand how those planets form, what they are made of (e.g. are they rocky or are they water world?), and whether some of them might be hospitable to life.

I conduct mainly theoretical work using computer simulations to model the formation of planetary systems. I use Mercury codes for N-body simulations, the Pencil Code for hydrodynamic simulations, and I am generally interested in scientific computing. The movie below shows one of my simulations. Here, 125 planetary embryos (red circles) are embedded in a protoplanetary disk (gray). The color of each circle shows the gas fraction of each planet. Planets accrete gas from the disk, and lose gas when they have a giant collision with another planet.

What’s happening in the video: At the beginning the embryos have strong gravitational interactions that lead to many collisions as well as high orbital inclinations and eccentricities. Meanwhile the protoplanetary disk works to dampen the eccentricities and inclinations. After about a million years, the planets settle into a chain of mean motion resonances. Additional interactions with the disk cause the planets to lose angular momentum and migrate toward the star. By dampening the eccentricities and inclinations, the gas disk also helps stabilize the system. After 5 million years, the disk disappears and the system becomes dynamically unstable. This leads to another phase of collisions that results in a planetary system with a smaller number of more massive planets no longer in resonance.

Education

Ph.D., Astronomy & Astrophysics, Lund University, 2017.
Thesis: Formation and Early Evolution of Planetary Systems.

M.S., Astronomy & Astrophysics, Lund University, 2012. Graduated with Distinction.
Thesis: The effect of dark matter capture on binary stars.

B.Sc., Math & Physics, University of Toronto, 2001. Graduated with Distinction.

Publications

Carrera, D., Ford, E. B., Izidoro, A., Jontof-Hutter, D., Raymond, S. N., & Wolfgang, A., “Identifying inflated super-Earths and photo-evaporated cores”, 2018, ApJ, 866, 2

Carrera, D., Davies, M.B., Johansen, A., “Toward an initial mass function for giant planets”, 2018, MNRAS, 478, 961.

Yang, C.-C., Johansen, A., Carrera, D., “Concentrating small particles in protoplanetary disks through the streaming instability”, 2017, A&A, 606, A80.

Carrera, D., Gorti, U., Johansen, A., Davies, M.B., “Planetesimal Formation by the Streaming Instability in a Photoevaporating Disk”, 2017, ApJ, 439, 16.

Carrera, D., Davies, M.B., Johansen, A., “Survival of habitable planets in unstable planetary systems”, 2016, MNRAS, 463, 3226.

Carrera, D., Johansen, A., Davies, M.B., “How to form planetesimals from mm-sized chondrules and chondrule aggregates”, 2015, A&A, 579, 43.