Research Highlights

How does the star forming environment affect nascent planetary systems?

The collapse of interstellar dusty gaseous star-forming clouds with some rotation naturally produces circumstellar planet-forming disks - the progenitors of planetary systems like our own Solar System.

The properties of these planet-forming disks are thought to be inherited from their parent clouds such that star and planet formation are inextricably linked and mediated by processes within these circumstellar disks.

Recent observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA) have focused on observations of dusty older stage disks in hopes of seeing the beginning stages of forming planetary systems. These observations have yielded that many protoplanetary disks are not smooth and featureless, but instead are rife with substructure in the form of spirals, rings, and gaps, many of which are likely due to the perturbations of forming planetary bodies.

However, a recent census of planet forming materials, dust and gas, has found that these later stage objects are relatively depleted in these planetary building blocks. This suggests that planet formation could be occurring at much earlier phases than previously thought. Which leads to the question:

How does infalling material during the embedded phase mediate disk substructure and the resulting disk dynamics?

Methodolgy

My research methodology is centered around exploring the physics of star and planet formation with the aid of a mixture of numerical methods (e.g. N-body, SPH, hydrodynamic grid codes).

TOP: Stars and their planetary systems form within clusters, embedded in and subject to the dynamics of their environments - interstellar dust, gas, and other protostars.
TOP: Stars form over short dynamical timescales in this cold collapse cluster formation simulation with the SPH code Gadget2. The free-fall time < 1 Myr for this Orion-like embedded cluster. Gas particles are shown in red with the forming sink (star) particles as green open circles.(Kuznetsova et al, 2015)
BOTTOM: Protostellar core behavior for a sample core in our Athena simulations, tracking the specific angular momentum, accretion rate, magnetic field magnitudes and the directional changes they under go over time as a result of directional and episodic accretion. (Kuznetsova et al, 2020)

Motivating work: Top-down cluster formation simulations

The objective of my thesis (2020, supervised by Prof. Lee Hartmann at the University of Michigan) was to to identify and understand the dominant physical processes that dictate disk properties and behavior through the use of large scale star cluster formation simulations.

Top-down cluster formation simulations allowed us to statistically characterize protostellar systems and understand the role of global gravitational collapse in assembling realistic cluster environments (see Kuznetsova et al, 2015, 2017, 2018a).

We found that gravitational focusing - a process in which mass accretion onto an object scales with the mass of the object, also called Bondi-Hoyle-Lyttleton accretion, shapes the mass function of cluster objects, both at large scales for the star cluster mass function (Kuznetsova et al, 2017) and the stellar initial mass function (Kuznetsova et al, 2018b).


By tracking the properties of accretion (mass, angular momentum, magnetization) onto protostellar cores in a suite of simulations with the MHD code Athena (see Kuznetsova et al, 2018b, 2019, 2020), we found that protostellar cores form in highly dynamic environments which characterizes the accretion onto these systems as highly episodic and directional.

What does this mean for disk and planet formation?

This kind of accretion has the potential to easily create structured, dynamically interesting (i.e. RWI, GI capable) disks that could lead to planet formation at much earlier phases than previously thought!