The Caltech Astronomy Graduate Program

Aims and Scope

The Caltech Astronomy graduate program aims to prepare students for creative and productive careers in astrophysical research and to train the next generation of leaders in the field. While the vast majority of our graduate students come from undergraduate astronomy or physics programs, some arrive with related majors such as engineering. In addition to those admitted directly to Astronomy, students in Physics who have astrophysical interests may conduct research with Astronomy or Physics faculty. Conversely, Astronomy students may also take the opportunity to work with faculty in either department. A discussion of the Astronomy option is contained in the following text; for more information on the Physics option, refer to the Caltech website.


Incoming students have a solid background in physics, and although good preparation in astronomy is helpful, this is not required for admission. All applicants, including those from foreign countries, submit Graduate Record Examination scores for the verbal and quantitative aptitude tests plus the advanced test in physics. Letters of recommendation, a personal statement, and transcripts round out the application package.

“I couldn’t have asked for a better combination of incredible research opportunities and life-long friendships.”
Alumna Alice Shapley (Ph.D. 2003)
Associate Professor, UCLA

Academic Program

In astrophysics, we strive to understand the physical processes that govern the universe, its constituents, and their evolution. We use the apparatus and methodology of physics to gather and interpret data and to conduct theoretical studies. Caltech Astronomy students are embedded in a large and diverse department with interesting talks, seminars, and conferences happening nearly every day. This helps them acquire broad knowledge and good scientific practices. They receive intensive classroom training, including exposure to all aspects of modern astrophysics.

There are six astronomy classes to be completed during the first year of graduate study: Radiative Processes, Structure and Evolution of Stars, Structure and Dynamics of Galaxies, High-Energy Astrophysics, Interstellar Medium, and Cosmology and Galaxy Formation.

Also during their first or second year, students focusing on observational astronomy take the Astronomical Measurements and Instrumentation sequence and four courses in physics or another appropriate subject. Theory students, on the other hand, select six classes in physics, mathematics, or other applicable fields. All first-year students participate in Introduction to Modern Research which exposes them to available research opportunities.

“Astronomy training is excellent preparation for many real-world careers, such as quantitative finance, in which you have to make judgments in situations with lots of uncertainty. My graduate education at Caltech gave me valuable skills in interpreting noisy data, applying inevitably incomplete models to make as robust inferences as possible, and, most importantly of all, appreciating the limits of the conclusions that can be drawn from the combination of less-than-perfect data and models.”
Alumnus Todd Small (Ph.D. 1996)
Research Associate, First Quadrant, LP

After their first year, students are encouraged to enroll in upper-level special topics courses, which are offered according to student demand and professor interest. All students second-year and beyond take a Journal Club seminar to hone their presentation skills. For more information on courses, please see

As with most graduate departments, Caltech has a qualifying exam. Here, the exam is an hour-long oral examination given at the start of the second year and focused on the required first-year astronomy courses plus a presentation on the student’s first-year research.

After passing the qualifying exam, graduate students transition to teaching-assistant positions for the duration of their second year. The teaching assignments are made by the students themselves and include assisting with courses ranging from first-year graduate classes to undergraduate lectures, recitations, and laboratory classes at all levels. After the one-year teaching requirement, most students move to full-time research positions.

For students interested in mentoring and teaching, there are additional opportunities to help lecture for courses or to continue working as a teaching assistant‚ especially for the freshman-level introductory astronomy class. In addition, graduate students often co-mentor summer students through the Caltech Summer Undergraduate Research Fellowship (SURF) Program.


The graduate program emphasizes independent research, and students are free to pursue study in virtually any area of astrophysics. They are encouraged to sample several different research projects before embarking on their thesis work. Research may be supervised by any of the teaching or research faculty, and can be performed in collaboration with postdocs or larger consortia. Faculty members advise, on average, 2 postdocs and 1-2 advanced graduate students (3rd through 5th-year) as well as the 1st and 2nd-year students collectively. Many also take on one or more undergraduate students each summer.

““Even now Caltech feels like home to me, with some of the most intellectually inspiring and fun-loving people I've ever known.”
Alumnus Ben R. Oppenheimer (Ph.D. 1999)
Associate Curator and Professor
American Museum of Natural History
Columbia University

Caltech's extensive, world-class observational facilities have always been an important component of our graduate education program, and our students learn the trade from the active example of their peers and advisors. The access they have to develop and use these observatories is simply unmatched by any other institution. Our deep connections to the JPL and the "Greater IPAC" communities, which develop and operate space missions (such as Spitzer, Herschel, and WISE), add to the large list of opportunities open to the students. To match its unparalleled observational resources, Caltech has an excellent theoretical astrophysics group – TAPIR – shared by the Physics and Astronomy departments. Students in TAPIR work alongside leading scientists in many venues of theoretical astrophysics and also benefit from collaborations with leading observers and instrumentalists.

Thesis Projects

Many Caltech theses represent substantial, even milestone, results in their fields and position our graduates for continuing careers of excellence. Eighty percent of our graduate program matriculates receive Ph.D. degrees, within a mean time of 5.5 years. Students who graduate from Caltech with an M.S. degree generally find employment in education, research, or industry.

Recent examples of Ph.D. theses reflect the breadth and diversity of research pursued by students at Caltech. In the realm of theoretical astrophysics, Eugene Chiang (Ph.D. 2000) crafted theoretical models for the emission of proto-planetary disks surrounding young stars. Hilke Schlichting (Ph.D. 2009) completed theoretical studies of planet formation and early solar system while using data from the Hubble Space Telescope to set a limit on the number of small bodies in the Kuiper belt. Theoretical investigations of weak gravitational lensing by dark matter concentrations were pursued by Nevin Weinberg (Ph.D. 2005). Margaret Pan (Ph.D. 2006) studied the dynamics of planetary systems and relativistic shocks emerging from stellar envelopes. The physics of the early universe was studied by Adrienne Erickcek (Ph.D. 2009), who investigated the role of inflation and its imprints on the cosmic microwave background.

“The unmatched access to astronomical facilities and research opportunities fuels independent research by Caltech's graduate students from day one. By accelerating the learning process associated with leading a research project, I have been able to attract students and collaborators with greater ease as I move forward in the profession.”
Alumna Alicia Soderberg (Ph.D. 2007)
Assistant Professor, Harvard University

In the realm of observational astrophysics, Dan Stark (Ph.D. 2008) discovered several galaxies that formed in the first 2 billion years after the Big Bang, and George Becker (Ph.D. 2006) used studies of the cosmic evolution of intergalactic hydrogen to argue that the reionization era lasted longer than 2 billion years. The detailed manner in which the first galaxies grew in mass due to smaller galaxies coalescing was investigated by Kevin Bundy (Ph.D. 2006), while Alice Shapley (Ph.D. 2003) studied the properties of star-forming galaxies when the universe was just a small fraction of its current age. Josh Bloom (Ph.D. 2002) established the connection between gamma-ray bursts and supernova explosions. New insights into the physics of gamma-ray bursts were provided by Edo Berger (Ph.D. 2004), who identified a common energy source for the most extreme of these events. Constraints on the polarization of the cosmic microwave background radiation were obtained by John Cartwright (Ph.D. 2002). The first well-recognized brown dwarf was discovered as a companion to a nearby star by Ben Oppenheimer (Ph.D. 1999). Francis O'Donovan (Ph.D. 2007) measured tiny periodic variations in the brightness of nearby stars to discover several of the first transit events by extra-solar planets. Meanwhile, Joanna Brown (Ph.D. 2007) obtained the first direct images of circumstellar disks with inner holes, a sign of disk evolution and possibly planet formation.

Progress in astronomy relies upon the invention and implementation of new instruments. Stuart Corder (Ph.D. 2008) Research played a substantial role in the commissioning of the CARMA array; his thesis contained some of its first results, revealing infall of molecular gas into a massive protostar. Josh Eisner (Ph.D. 2005) motivated new uses of the Palomar Testbed and Keck Interferometers. Ben Mazin (Ph.D. 2004) made significant progress in developing Microwave Kinetic Inductance Detectors (MKIDS), which are expected to revolutionize detector technology from sub-millimeter to X-ray wavelengths in the next few years.

These are a small sample of the revolutionary developments enabled by the ingenuity of the Caltech students and faculty, and by the observational and theoretical resources of the Institute.

Alumni & Job Placement

Caltech Astronomy boasts a long and impressive list of Ph.D. alumni who have gone on to distinguished careers in the field. Details on many graduates of the program are listed on our website along with their current employment and links to archived theses.

“My time as a graduate student at Caltech gave me an exposure to the front-line of astronomy research. I bring my experiences observing at world-class facilities and interacting with the tremendous people at Caltech into my classes, giving my students a feel of the way astronomy really works! I believe that a Ph.D. from Caltech helps open doors into education.”
Alumnus Micol Christopher (Ph.D. 2008)
Professor, Mt. San Antonio College

Overall, our graduates do very well in the postdoctoral job market, and typically several per year win prestigious fellowships. The long-term research employment prospects for Caltech Astronomy Ph.D.s compare very favorably with those at other institutions (see figure). For instance, when compared to the national average, we have placed a higher percentage of our Ph.D.s into highly competitive faculty positions at research universities.

Among alumni graduating over the past 30 years, close to half (47%) have found long-term employment as professors at Ph.D.-granting universities, with an additional 34% employed as staff at observatories or national laboratories. 13% are in business or industry, 2.5% are professors at 4-year or community colleges, and another 2.5% work in other education-related careers.

Nationally, while the number of bachelor's degrees in astronomy was within 15% of constant throughout the 1980s and 1990s, over the past decade there has been close to 100% growth in the number of astronomy majors and 60% growth in physics majors. The increased pools for graduate admission have been accompanied by a smaller yet very substantial 50% increase in the number of available first-year graduate student positions nationwide. At the same time, the number of doctorate degrees awarded has remained stable (+/-15%).

As an observational astronomer, Caltech offered me research opportunities that were unparalleled at any other graduate school. I've led programs that work with observations from Hubble, Keck, Palomar, HET, and the VLT, and I've presented the results of those programs at many conferences around the world.
Alumnus Adam Kraus (Ph.D. 2009)
Hubble Postdoctoral FellowInstitute for Astronomy at the University of Hawaii

At Caltech we typically graduate between 2 and 6 Astronomy Ph.D.s per year, and a similar number of Physics graduate students whose primary interest is astrophysics. Our matriculating first-year class in Astronomy ranges from year to year between 2 and 9 students. Presently in Astronomy, there are 25 graduate students. We also have 2-5 undergraduate majors per year. Almost all of our undergraduate majors participate in summer research here at Caltech, and one-half to two-thirds go on to graduate school in astronomy or physics.

Caltech graduates often maintain active collaborations with the faculty and staff at Caltech, even long after their graduation.

[Image credits: The David and Lucile Packard Foundation; Todd Small; Ben Oppenheimer; Princeton Media Office; Micol Christopher; Gwen Rudie]