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


Research: Formation and evolution of exoplanet systems

I am an Assistant Research Professor at the Center for Exoplanets and Habitable Worlds at Penn State. I study the formation and evolution of planetary systems, including the origin of water and atmosphere in super-Earths, and their potential 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. 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 worlds?), 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.


Explanations for the movies are shown after the carousel:

Movie explanations

  • Formation of super-Earths
    The first six movies show the formation of a Kepler-like system with multiple super-Earths with short orbital periods. The simulations begin with 125 planetary embryos that first experience strong gravitational interactions and collisions. After about 1 Myr, the embryos merge into a smaller number of planets which settle into the midplane of the disk due to planet-disk interactions. Planets migrate and become locked into chains of mean motion resonances. Most of these chains would be dynamically unstable were it not for the effect of the disk dampening the orbital eccentricities. When the inner chain reaches the edge of the disk, the torque on the planets farther out force the inner planets to push past the disk edge, leading to the formation of planets with very short orbital periods.

    This work is presented in Carrera et al. (2019a) and Carrera et al. (2018b).

  • Survival of habitable planets in unstable planetary systems
    The next two movies show the possible fate of a rocky planet in the habitable zone of a planetary system where planets become dynamically unstable. The giant planets have the mass of Jupiter, Saturn, Uranus, and Neptune, but they have smaller orbits which enhance the effect of planet-planet gravitational interactions. The habitable zone is shown in green. The evolution of the system is chaotic; small changes in the initial conditions can lead to vastly different outcomes. In one simulations, the instability is benign and most habitable planets survive. In the other simulation, the giant planets experience a catastrophic instability that completely decimates the habitable zone.

    This work is presented in Carrera et al. (2016).

  • Planetesimals formation by the streaming instability
    The last two movies show the behaviour of pebbles, or small solid particles, embedded in a protoplanetary disk. The particle-gas drag leads the solids into dense filaments. These dense filaments may be the birthplace of planetesimals. In this investigation I ran a wide range of simulations with different particle sizes and densities, and I measured the density needed to trigger the streaming instability (and form dense filaments) as a function of particle size.

    This work is presented in Carrera et al. (2015).


Carrera, D., Ford, E. B., & Izidoro, A., 2019, MNRAS, “Formation of short-period planets by disc migration”, 486, 3874

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.


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.