A Brief Synopsis of my Graduate Research
Alternatively, you can read the full, detailed synopsis here:
A Distant Dwarf Planet Candidate named DeeDee
Mining a new dataset is bound to yield some exciting discoveries, and sure enough, we found some cool things! The discovery near and dear to me was of a new distant dwarf planet candidate that I nicknamed DeeDee (for “distant dwarf”). How distant? 92 astronomical units (Earth-Sun distances, aka “au”) from the Sun, or 2.5x farther than Pluto!
At the time, DeeDee was the second-most distant Solar System object ever discovered. And when we discovered it, we didn’t know how big it was. All we saw was a point of light in the images, but we didn’t know whether that point of light was small and shiny or large and dark. I led a telescope proposal for ALMA to get immediate supplemental infrared data and then led the analysis to calculate DeeDee’s size using the extra data. DeeDee is about 640km in diameter (about the size of Oregon) and reflects about 13% of the light that hits it (like asphalt or a dark roof).
This analysis provided another data point about intermediate-sized bodies in the Kuiper Belt, filling in the complete picture a bit more like filling in a TV screen a few pixels at a time. The discovery also proved that we could discover very distant objects, which is relevant for the next section…
Planet Nine…does it exist or not?
Planet Nine is a proposed, still-hypothetical distant planet beyond Neptune. It’s thought to be about 5 Earth-masses and on a distant, elliptical orbit with an average distance from the Sun of 250au (for context, Neptune is about 17 Earth-masses and orbits the Sun at an average distance of 30au).
Why do some astronomers think it’s there? We haven’t found it directly, so the evidence for its existence is purely mathematical at this point. Based on the fact that the orbits of the most distant trans-Neptunian objects (those that orbit at an average distance of >250au, aka “extreme” TNOs or ETNOs) all appear to be oriented in the same direction, astronomers Mike Brown and Konstantin Batygin predicted that a new planet’s gravitational influence was the culprit.
How do we know that the apparent orbital orientation is real and isn’t just an artifact of where we happen to search and find these objects? Well…we don’t. And this has been a source of debate since Planet Nine’s proposal in 2016. To quantify whether the effect is an artifact, we need a survey simulator — effectively a way to simulate the detection and discovery of thousands of artificial objects in order to understand exactly which types of objects the survey is more/less likely to discover and where.
I built a survey simulator of the Dark Energy Survey in order to statistically test whether Planet Nine’s signature was present in our sample of four extreme TNOs. Unfortunately, a sample size of four is just not big enough to make any conclusive claims, so our sample neither refutes nor confirms Planet Nine. My colleague Kevin Napier has expanded upon my work to include two additional surveys, bringing the sample size to 12, but this still is not a large enough sample to make conclusive claims. Bottom line: we need more data!
Other Kuiper Belt research
The survey simulator that enabled me to study the most distant TNOs in the context of Planet Nine also enabled me to study other Solar System objects in a greater context. Here are some of those objects:
- 2015 BP519, aka "Caju"
The most "extreme" of the extreme TNOs, partially due to its high inclination of 54°. This object's existence is potentially a strong piece of evidence for Planet Nine. - Two new Neptune trojans, including the first ultra-red trojan
The prior absence of an ultra-red population was a problem for models of solar system formation. I quantified the Dark Energy Survey's likelihood of discovering such an object and predicted a ultra-red-to red ratio of 17:1. - Three potentially-related extreme TNOs
The Dark Energy Survey discovered three extreme TNOs with very similar orbits. I quantified the likelihood of finding this (not super likely). - Ground-based search and discovery for New Horizons
I initiated our group's partnership with New Horizons and contributed to telescope proposals to search for new observational targets for the spacecraft.
Selected Publications
“Testing the isotropy of the Dark Energy Survey’s extreme trans-Neptunian objects,” 2020, P. H. Bernardinelli, et al (incl. S. J. Hamilton as co-corresponding author), arXiv:2003.08901, Planetary Science Journal, doi:10.3847/PSJ/ab9d80.
“New Science, New Media: An Assessment of the Online Education & Public Outreach Initiatives of The Dark Energy Survey,” 2018, R. C. Wolf, et al (incl. S. J. Hamilton), arXiv:1804.00591.
“Evaluating the Dynamical Stability of Outer Solar System Objects in the Presence of Planet Nine,” 2017, J. C. Becker, F. C. Adams, T. Khain, S. J. Hamilton, D. W. Gerdes, et al, arXiv:1706.06609, Astronomical Journal, doi:10.3847/2041-8213/aa64d8.
“Discovery and Physical Characterization of a Large Scattered Disk Object at 92 AU,” 2017, D. W. Gerdes, M. Sako, S. J. Hamilton, et al., arXiv:1702.00731, Astrophysical Journal Letters, doi:10.3847/2041-8213/aa64d8.
*For complete list, please see NASA ADS.
Research History
PhD Research Fellow
University of Michigan
2015—2019
Developed, studied, and characterized new Kuiper Belt Objects using data from the Dark Energy Survey. Measured the size of the second-most-distant solar system object, the dwarf planet candidate DeeDee. Lead code architect of a survey simulator to characterize discoveries in the context of the full Solar System. >30 nights of telescope operation experience, >25 as run manager.
Graduate Research Assistant
University of Michigan
Summer 2014
Co-developed liquid nitrogen cooling system for a liquid xenon dark matter detector prototype that improved cooling time by >70%. Developed and maintained data analysis code.
Undergraduate Researcher
Michigan State University
2010—2014
Initiated preliminary analysis on simulated Higgs boson events in order to understand the physics happening at the Large Hadron Collider. Developed parameter optimizations to better distinguish between Higgs vs. non-Higgs particle interactions. Developed data pipeline improvements to identify and discard corrupted data that passed prior checks.
Summer Intern
Fermilab
Summer 2013
Led development and implementation of C++ code that allowed for the simultaneous optimization of many parameters of a multivariate discriminator used in a Higgs boson analysis.
Summer Intern
CERN
Summer 2012
Led efforts to identify origin of and implement new data filters for rare instances of corrupted data in one portion of the ATLAS detector at CERN, the Tile Calorimeter. Project continued into 3rd year at Michigan State. Witnessed discovery announcement of Higgs boson in person!
Summer Intern
Fermilab
Summer 2011
Developed, implemented, and tested new kinematic variables to add to a multivariate Higgs boson analysis. Contributions resulted in >10% improvement to an already-mature analysis.