I'm James Johnson

Astrophysicist at Carnegie Observatories


"To confine our attention to terrestrial matters would be to limit the human spirit."
-Stephen Hawking

Galaxy Evolution

Galaxies formed out of the gravitational collapse of matter in the primordial universe. How do the details of this process relate to the observed properties of galaxies at the present day, such as mass and morphology?

The Milky Way

Despite our position within the Milky Way, many details of its assembly history remain unknown. What are the star formation and dynamical histories of our Galaxy? What is its assembly history? How does this relate to its detailed chemical composition?

The Origin of the Elements

The Big Bang left behind only hydrogen, helium, and trace amounts of lithium; everything else was produced in stars. How much of each element is produced by stellar populations? How does this depend on the mass of a star and its chemical composition? Which stars explode as supernovae at the ends of their lives?

Astronomical Software

In the modern era, astrophysics is aided by computers at every step of the way, from observations with telescopes to theoretical modeling. As a lifelong computer nerd, I dedicate a portion of my time to building fast and efficient software tools for both collaborators and the broader astronomical community.


"The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires."
-William Arthur Ward
From Planets to Cosmos
The Ohio State University
Teaching Assistant
5 sections
Planets & the Solar System
The Ohio State University
Teaching Assitant
1 section
Astronomy Data Analysis
The Ohio State University
Teaching Assistant
1 section
Black Holes
The Ohio State University
Teaching Assistant
1 section
Principles of Physics I & II
Vanderbilt University
Undergraduate Tutor, Proctor, Grader
6 semesters

Python Bootcamp

Looking to improve your python programming? In this bootcamp, you can find instructional material covering:
  • Review of the Fundamentals: built-in data types, conditionals, loops, functions, exceptions
  • Multi-file programs and basic package structure
  • Object-oriented programming
  • Aliases and environment variables in the Unix terminal


"The way a team plays as a whole determines its success. You may have the greatest bunch of individual stars in the world, but if they don’t play together, the club won’t be worth a dime."
-Babe Ruth
Thesis Committee
David H. Weinberg
[Distinguished Univ. Prof., Ohio State]
Jennifer A. Johnson
[Professor, Ohio State]
Christopher S. Kochanek
[Professor, Ohio State]
Students and Mentees
Daniel Boyea
[Undergraduate Student, Ohio State]
Liam O. Dubay
[Graduate Student, Ohio State]
Miqaela Weller
[Graduate Student, Ohio State]
Other Collaborators
Charlie Conroy
[Prof. of Astronomy, Harvard University]
Emily J. Griffith
[NSF Postdoctoral Fellow, CU Boulder]
Jonathan C. Bird
[VIDA Postdoctoral Fellow, Vanderbilt Univ.]
Krzysztof Z. Stanek
[Professor, Ohio State]
Ari Bredall
[Graduate Student, Ohio state]
Ryan J. Cooke
[Assoc. Prof., Durham Univ.]
Fiorenzo Vincenzo
[Asst. Prof., Univ. of Hull]


"The success of your presentation will be judged not by the knowledge you send but by what the listener receives."
-Lilly Walters
These are the slides from my dissertation talk at the 241st meeting of the American Astronomical Society in Seattle!
I gave this talk at the 2021 SDSS Collaboration Meeting, held virtually. I gave a talk with similar content at the 2021 GALAH Science Meeting - check out the YouTube recording!
I gave this talk at the 2020 SDSS Collaboration Meeting, held virtually.
I gave this talk in the Inter[stellar+galactic] Medium Program of Studies Seminar at the University of California Santa Cruz Department of Astronomy in May of 2019.

Diversity, Equity, and Inclusion

"Space is for everybody. It's not for a few people in science or math, or for a select group of astronauts. That's our new frontier out there, and it's everybody's business to know about space."
-Christa McAuliffe
As a graduate student, I served on the leadership committe of Polaris, an entirely graduate student led organization dedicated to fostering a more inclusive environment and improving the retention of students from disadvantaged backgrounds in Physics and Astronomy at Ohio State. To this end, Polaris focuses on fostering a sense of belonging, developing a science identity, and improving self-efficacy among students.
Polaris's first and foremost initiative is its mentorship course offered to students in their first two years of Ohio State math, physics, and astronomy bachelors programs. While initiating discussion about the status of diversity in STEM, this course also pairs students with graduate and upper-level undergraduate mentors who will help them learn to maintain a mentor-mentee relationship, develop goals, communicate effectively, and harness mentorship as a pathway to academic excellence.
The Undergraduate Residential Summer Access (URSA) early arrival program takes place every summer in the two weeks leading up to the start of fall semester classes. Offered to incoming first-year and transfer students, URSA aims to build a cohort among the incoming students and familiarize them with Ohio State's campus to ease their transition to university-level academics. URSA also introduces the students to various research programs in Ohio State physics and astronomy and discusses how diversity and equity might impact their experience as rising STEM students.
As a graduate student, I was also a regular participant of Ohio State Astronomy's Diversity Journal Club, a recurring meeting focused on the issues of diversity, equity, and inclusion not only in astronomy and astrophysics, but in academia as a whole. With dedicated time for discussion, these seminars also focus on steps individuals and departments can take to improve the current situation facing minority groups.

Curriculum Vitae

"Anyone who has never made a mistake has never tried anything new."
-Albert Einstein
Academic Appointments
2023 - Present
The Observatories of the Carnegie Institution for Science
Postdoctoral Fellow, Carnegie Theoretical Astrophysics Center
Supervisor: Ana Bonaca
2017 - 2023
Ph.D. in Astrophysics, The Ohio State University
Dissertation Advisor: David H. Weinberg
2013 - 2017
B.A., Vanderbilt University
Physics major, Astronomy minor,
cum laude

Highest Honors in Astronomy; Thesis Advisor: Andreas A. Berlind
CTAC Postdoctoral Fellowship
The Observatories of the Carnegie Institution for Science
Ann S. Tuttle Graduate Student Paper Prize
The Ohio State University, Dept. of Astronomy
Top graduate student led paper of previous year
Presidential Fellowship
The Ohio State University
Financial support for final year Ph.D. candidates
Graduate Fellowship
The Ohio State University
Financial support for first-year graduate students
Larry Ross Cathey Award
Vanderbilt University, Dept. of Physics & Astronomy
Outstanding senior studying astronomy

Research Metrics

Journal Publications
Talks & Seminars

About Me

"Astronomy compels the soul to look upward, and leads us from this world to another."
Iowa City, Iowa
1995 - 1997
Lincoln, Nebraska
1997 - 2013
Nashville, Tennessee
2013 - 2017
Columbus, Ohio
2017 - 2023
Pasadena, California
2023 -
I am a postdoctoral fellow at Carnegie Observatories in Pasadena, California. I recently earned my Ph.D. from The Ohio State University, where Professor David H. Weinberg served as my dissertation advisor. I previously earned my Bachelor's from Vanderbilt University, where I did my undergraduate honors thesis with Professor Andreas A. Berlind.

Hailing from the American midwest, my fascination with space began during my childhood and was nurtured by rural Nebraska's dark skies. Coming from a family of healthcare providers, I began my undergraduate career studying pre-medicine before pursuing astrophysics.

Beyond astronomy, I enjoy traveling, cooking, playing video games, watching sports, and playing guitar. I am also a fluent German speaker, having lived and studied in Berlin in 2016.

Contact Me

Have a research question you'd like to discuss?