Graduate Student Spotlight: Chris Johnson, LSU Department of Physics & Astronomy

photo: graduate student spotlight chris johnson

LSU Astronomy PhD Candidate Christopher Johnson exemplifies the best of the Graduate Student Research Assistance (GSRA) program, supported by the Louisiana Space Consortium

(LaSPACE). Chris has received consecutive GSRA awards in support of his exemplary research and commitment to professional development. Each award has supported travel to collaborative meetings and scientific conferences, which led to invitations to participate in additional scientific meetings, thus increasing Chris’s experience, professional network, and communication skills while presenting his work.

Chris shares some details about his research and advice for students looking to attend LSU Graduate School.

I am primarily interested in the physics that is involved with the evolution of black holes and white dwarfs and the objects that orbit them. A black hole is characterized as the end stage of a massive star that has collapsed in on itself after a supernova outburst so that nothing, not even light, can escape the immense gravitational pull. A white dwarf is referred to as the end stage of a low mass star, much like our own Sun. At this point, the star has collapsed in on itself to where, at the atomic level, the only thing that is overcoming the gravitational force inward is the compacted electrons occupying every facet of space in the stellar core. This is known as the electron degeneracy pressure and is the basis for degenerate matter. 

I use photometry and spectroscopy of these systems to essentially “weigh the stars.” That is, if we look at the brightness variations of a system over time, we can construct a light curve and infer a period for the system, ideally from eclipses or sinusoidal motion. Using this orbital period along with the radial velocity of the system given by the absorption spectral features and the Doppler shifts of these features, I apply Kepler's Laws of Motion and calculate a mass for the system. The mass is one of the most important parameters that can be measured for stellar systems, especially black holes, since there are only a handful of black holes confirmed out of the many, many billions of objects in the Universe. Understanding the mass distribution of these systems allows us to infer how and when they formed, where they formed, and how they evolve over time. Many scientific teams have been working on these problems for 50 years and yet there are still more questions than answers concerning black holes.

Tell us a little about yourself.

I was born and raised in Detroit, Michigan and then moved to Tucson, Arizona where I attended the University of Arizona and received my BS in Physics. I received my MS in Physics from LSU and will graduate with my PhD this summer. I have accepted a NASA-funded, Postdoctoral Fellowship in the Science Mission Office at the Space Telescope Science Institute at Johns Hopkins University in Baltimore, Maryland beginning in the fall of 2016. I will be a data scientist analyzing large data sets from space telescopes, primarily the Hubble space telescope.

What have you enjoyed most about the graduate program in Physics & Astronomy at LSU?

I believe that the best part about the PhD program is that graduate students have the opportunity, and are encouraged, to travel and promote their own research at conferences and attend summer schools to gain further experience in their particular field of interest. The physics and astronomy community is very close-knit, so creating networks for collaborations and potential future employers is critical. 

What is the best advice you would give someone thinking about pursuing graduate school?

Pursuing graduate school is not an easy choice to make and there is not a perfect answer to whether one should attend or not. It is wonderful at times and also the most stress you will ever experience in your life. What it comes down to is whether you are passionate enough to devote a portion of your life to a particular field of study in hopes of helping advance that field and (someday) becoming an expert on the topic.
-Chris Johnson
For more details on his work, he recommends the following articles: Johnson, C. B. et al. 2014, MNRAS, 444, 2, p.1584 and Johnson, C. B. et al. 2014, ApJ, 780, 2, L25.

About the Graduate Student Research Assistance (GSRA) program
The Graduate Student Research Assistance (GSRA) program is designed to augment compensation levels available to promising graduate students on LaSPACE campuses and, thereby, 1) retain more U.S. students for graduate study at consortium institutions, 2) promote diversity, and 3) assist in dissertation research. The GSRA supplement is $8,000 for a 12-month period and can be used for augmenting the student stipend, to defray dissertation related research expenses, and promote student research presentations at national meetings. Cost share on the award is required as is a final technical report. Applications are judged on the basis of aerospace relevance of the research and overall relevance to LaSPACE research and human resource development objectives.


Mimi LaValle
LSU Department of Physics & Astronomy