Research Interests
Research Interests
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Planet Formation
Planet Formation
Explaining the remarkable variety of planets that encircle other stars requires that we study the early history of planets and how they interact with their natal environment, the circumstellar disk.
Do most stars possess disks massive enough to form planets?
How is material distributed radially and vertically in the disk? The density of material controls the timescales for planet formation, and the temperature and viscosity of the disk control the transport of solids.
How does disk material dissipate?
How do disks and planetesimals interact?
How do planets obtain their compositions and volatiles?
How do giant impacts shape planetary architectures and habitability?
Using the high spatial resolution and sensitivity of the Hubble Space Telescope and ground-based telescopes such as Magellan, I am studying dusty circumstellar disks as the birthplaces of planetary systems. The observations elucidate disk geometries and dust composition and in an ensemble fashion teach us about the evolution of disks and the timescales for planet formation within them. I try to connect the disks around other stars to our understanding of planet formation in our own Solar System and in other systems.
Disk Imaging
Disk Imaging
Visual and near-infrared imaging provides detailed morphologies and colors of resolved disks. I have been PI or co-I on many ground-based and HST programs over the years to image disks, particularly nearby dusty debris disks. Debris dust arises from the collisions and evaporation of planetesimals, and it is these same planetesimals which are the building blocks for planets (e.g. Debes et al. 2017). The goal is to be able to estimate the organic-to-silicate-to-refractory-ice ratios of the dust to constrain the place of formation and subsequent processing. By studying the grain composition directly with spectroscopy over a range of distances from the star, I try to learn about the processes of planet building and collisions that occur in disks. (e.g. Lomax et al. 2018, Arnold et al. 2018, Kueny et al. 2026).
MagNIFIES is a single-object, seeing-limited, high-resolution, near-infrared spectrograph. We will commission and use it on Magellan starting in 2030, in preparation for its ultimate deployment on the Giant Magellan Telescope as GMTNIRS.
MagNIFIES will deliver:
Wavelength Coverage: 1.08 - 5.4 μm simultaneously
High Spectral Resolution: 45,000 (1.08 - 2.45 μm) and 60,000 (2.9 - 5.4 μm)
World-class sensitivity: cryogenic immersion gratings and no moving parts
Irregular Dust Grain Models
Irregular Dust Grain Models
If the dust collected from comets in our own solar system is a good guide, the dust around other stars is irregular in shape. However, most studies of dust estimate how light (e.g. from a star) is scattered and absorbed by dust grains using Mie theory. Mie theory only applies to spherical grains. Light scattered from this simple morphology is fundamentally different from that of irregularly shaped dust grains, likely causing the mismatch between models and multi-wavelength images.
We have computed discrte dipole approximations of irregular grains over a wide range of compositions to provide high fidelity models for grains in a multitude of astrophysical environments. We have published the results of our models of irregular dust grains so that they may be used by the community, along with a public neural network trained to produce usable scattering properties so quickly that it can replace Mie theory calculations.
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