I am a third year Ph.D. candidate in the Department of Astronomy and a Research Assistant in the Center for Space Physics at Boston University. I work with Prof. Paul Withers at BU and Dr. Mike Person at MIT studying planetary atmospheres using stellar occultations.
I received my Masters of Arts in Astronomy from BU in 2020, on my way toward earning my PhD.
I received my Bachelors of Arts in Physics & Astronomy from the University of Pennsylvania in 2018, where I worked with Prof. n studying trans-Neptunian objects.
I am also co-host of the new podcast astro[sound]bites, which features posts on Astrobites.org, for which I have been a contributing writer since January 2019.
Current Research
Stellar Occultations
I currently work with Prof. Paul Withers at BU and Dr. Mike Person at MIT on stellar occultations of solar system objects.
A stellar occultation is when a nearby object (such as a planet or asteroid) passes in front of a star and obstructs the starlight from view on earth. Stellar occultations are used for a number of different scientific purposes:
Determine precise locations and sizes of trans-Neptunian objects.
Discover features like rings, volcanism, or moons around minor planets.
Measure features of planetary astmospheres.
Number 1 was how stellar occultations were used to determine the shape and position of Arrokoth before New Horizons flew past it.
Number 3 is what I work on.
The fundamental question of my research is how can we use a stellar occultation by Mars to learn details about the Martian middle atmosphere? In fact, through my research, I have measured the density, temperature, and pressure of Mars' atmosphere at very high resolution, which allowed me to detect small, moving waves.
One example of an occultation light curve, normalized to 1 before and after occultation and 0 during occultation. The gradual slopes at the beginning and end of occultation, which are difficult to see by eye, provide information about the atmosphere of Mars (Saunders et al., Submitted to AAS Journals).
How Does it Work?
As a star moves behind a planet's atmosphere, from Earth's point of view, the atmosphere acts like a giant lens, refracting the light from the star and causing it to spread out. This spreading out dims the star, creating a light curve. The red light curve is a real example from my research.
Using these light curves, we can use the rate of dimming of the star to measure the amount of "stuff" in the atmosphere that had to be present to cause it. The result is measurements of density, temperature, and pressure of the planet's atmosphere.
Temperature vs. pressure in the Martian atmosphere from stellar occultation of Mars. Note the large horizontal error bars. (Elliot et al., 1977)
The original result published in 1977 was the first atmospheric profile of Mars ever produced.
In my re-analysis of these data, I have three primary findings.
My higher-resolution results are consistent with models of the Martian atmosphere.
I detected internal gravity waves about 5 km vertical wavelength in the Martian atmosphere.
Re-analysis of archival data has singificant scientific merit.
In the 42 years between the original analysis and my re-analysis, there have been 7 Mars orbiters, 4 Mars landers, and 4 Mars rovers that have helped astronomers understand the Martian atmosphere much better. With this modern understanding and better computing techniques, I am able to confirm the reliabilty of my results and add to the understanding of the Martian atmopshere.
In April 2020, I submitted my first first-author paper "Re-Analysis of the 1976 Mars Occultation of Epsilon Geminorum: Detection of Gravity (Buoyancy) Waves" to AAS Journals.
Past Research
Search for Trans-Neptunian Objects
As an undergraduate physics major at the University of Pennsylvania I worked with Prof. Gary Bernstein using the Dark Energy Survey to identify trans-Neptunian objects (TNOs). TNOs are any solar system body beyond the orbit of Neptune and represent everything from well-behaved Kuiper Belt objects to poorly-understood scattering objects with unusual orbits.
Presenting my poster at AAS 231 in Washington, D.C. on Jan. 12 2018.
During the summer of 2017, I worked at NASA Ames Research Center on the formation of planetary systems with Dr. Uma Gorti. A protoplanetary disk is the dust and gas from which planetary systems form, but there is much uncertainty about how small dust grains can grow to planetessimals.
I used Uma's disk model to simulate how viscosity and photoevaporation impact the disk and found a range of parameters that allows the disk to keep enough mass to possibly form planets.
At the 231st meeting of the American Astronomical Society in January 2018, my first professional conference, I presented these findings.
Astrobites
Astrobites is a website run entirely by graduate students in astronomy and publishes daily summaries of recent astronomy publications. Astrobites is designed for undergraduate science majors to learn about the lastest work in astronomy in only a few minutes.
Some posts go beyond the traditional paper summaries, covering topics of applying for graduate school, student funding, and problems facing astronomy today. In November 2019, I published the first book review post for Astrobites, something I'm hoping becomes a new trend.
I wrote for Astrobites from January 2019 through December 2020. I currently serve as the Astrobites Undergraduate Co-Chair. Links to all my 14 Astrobite posts are below. My author page can be found at astrobites.org/author/wsaunders .
A simulation of the solar wind impinging directly onto Mercury, which might have been significant in causing Mercury to lose its mantle. (Spalding & Adams 2020) Dilhan Eryurt was the the first Turkish astronomer to work at NASA and the only woman at Goddard during her tenure. She fundamentally changed our understanding of the Sun.
I host the podcast astro[sound]bites, a spin-off of Astrobites, along with Malena Rice at Yale University, and Alex Gagliano at University of Illinois Urbana Champaign. Our new episodes every other week feature recent Astrobites centered around a theme in astronomy. We also go beyond research summaries, discussing topics about professional development, graduate student life, and more.
Working on a podcast has long been a dream of mine and I'm thrilled to be on the air. Find us on astrosoundbites.com, Apple Podcasts, Google Play, Spotify, and SoundCloud. We encourage listener feedback--email us at [email protected]
