Courses 2026-27: Astrophysics

Introduction to modern astronomy that will illustrate the accomplishments, techniques, and scientific methodology of contemporary astronomy. The course will be organized around a set of basic questions, showing how our answers have changed in response to fresh observational discoveries. Topics to be discussed will include telescopes, stars, planets, the search for life elsewhere in the universe, supernovae, pulsars, black holes, galaxies and their active nuclei, and Big Bang cosmology. A field trip to Palomar Observatory will be organized. Not offered on a pass/fail basis.

A broad introduction to the present state and early history of the solar system, including terrestrial planets, giant planets, moons, asteroids, comets, and rings. Earth-based observations, observations by planetary spacecraft, study of meteorites, and observations of extrasolar planets are used to constrain models of the dynamical and chemical processes of planetary systems. Although Ge 11 abcd is designed as a sequence, any one term may be taken as a standalone course. Physicists and astronomers are particularly welcome.

The electromagnetic spectrum; ground and space observing techniques; telescopes and basic astrophysical optics; orbits, binary stars and exoplanets; stellar masses and radii, distances, and motions; basic radiative transfer; the HR diagram; the birth, structure, evolution, and death of stars; the structure, contents, and dynamics of the Galaxy. A term project involving the Palomar 60" telescope will introduce astronomical measurement techniques.

Cosmological models and parameters, extragalactic distance scale, cosmological tests; constituents of the universe, dark matter, and dark energy; thermal history of the universe, cosmic nucleosynthesis, recombination, and cosmic microwave background; formation and evolution of structure in the universe; galaxy clusters, large-scale structure and its evolution; galaxies, their properties and fundamental correlations; formation and evolution of galaxies, star formation history of the universe; quasars and other active galactic nuclei, and their evolution; structure and evolution of the intergalactic medium; diffuse extragalactic backgrounds; the first stars, galaxies, and the reionization era.

Open to declared Ay majors. At the discretion of the instructor, nonmajors who have taken astronomy courses may be admitted. Course is intended for sophomores and juniors. This weekly seminar-style discussion is held in faculty homes in the evening, and is designed to encourage student communication skills as they are introduced to faculty members and their research. Each week a student will review a popular-level article or general topic in astronomy for the class. Fulfills the Institute oral scientific communications requirement. Graded pass/fail.

This course is intended to provide practical experience in the types of writing expected of professional astronomers. Example styles include: research proposals, topical reviews, professional journal manuscripts, and articles for broader audiences such as popular level magazines like Astronomy or Sky and Telescope. Each student will adopt one of these formats in consultation with the course instructor and write an original piece. An outline and several drafts reviewed by both a faculty mentor familiar with the topic and the course instructor are required. This course is most suitable for juniors and seniors. Fulfills the Institute written scientific communications requirement.

Course is intended for students with a definite independent reading plan or who attend regular (biweekly) research and literature discussion groups. Instructor's permission required. Graded pass/fail.

Previous SURF or independent study work can be useful experience. Course open to senior astronomy majors only. Research must be supervised by a faculty member. Students wishing assistance in finding an adviser and/or a topic for a senior thesis are invited to consult with the astronomy option representative. The student will work with an adviser to formulate a research project, conduct original research, present new results, and evaluate them in the context of previously published work in the field. In the first term, the student should be fully engaged in, and make significant progress on, the research project. In the second term, the research continues and an outline of the thesis itself should be reviewed with the adviser and the option representative. In the third term, research work continues to completion and the focus turns to thesis writing. A thesis document of 20-100 pages must be completed and approved by the adviser and the option representative before the end of third term. The student and advisor should maintain good communication regarding the scope, content, draft due dates, and final copy of the thesis. First two terms are graded pass/fail, with grades for all three terms updated at the end of the course to the final letter grade earned after thesis submission.

Physics of stellar interiors and stellar atmospheres. Stellar structure including nucleosynthesis in the cores of stars and energy transport. Stellar evolution. Fundamental properties of stars. The H-R diagram. Stellar spectra, radiative transfer, and spectral line formation. Additional topics may include: stellar oscillations, rotation, mass loss, binary evolution.

An introduction to observations of the interstellar medium and relevant physical processes. Phases of the gaseous interstellar medium. Thermal balance in neutral and ionized gas. Molecular gas and star formation. Hot ionized gas. Structure and hydrodynamic evolution of ISM regions near massive stars; supernovae shocks. Global models for the interstellar medium. Interstellar and circumstellar dust.

An opportunity for astronomy and physics undergraduates (juniors and seniors) to gain firsthand experience with the basic instrumentation tools of modern optical and infrared astronomy. The 10 weekly lab experiments include radiometry measurements, geometrical optics, polarization, optical aberrations, spectroscopy, CCD characterization, vacuum and cryogenic technology, infrared detector technology, adaptive optics (wavefront sensors, deformable mirrors, closed loop control) and a coronography tutorial.

This hands-on, project-based course covers the design, proposal, and execution of astronomical observations, the basics of data reduction and analysis, and interacting with astronomical survey catalogs. The scope of the course includes imaging and spectroscopic observational techniques at optical and infrared wavelengths. The format centers on projects and practical skills but also includes a lecture and problem set component to establish the theoretical underpinnings of the practical work. Specific course components include: (a) Students will learn to use small, portable telescopes and find and image objects of interest using finder charts; (b) Students will build basic data reduction pipelines for imaging and spectroscopy data to understand how these types of data are used to derive scientific results; (c) Students will use Palomar Observatory to propose and execute their own research projects focused on astrophysical or planetary topics; (d) Students will query and work with data from on-line archives and catalogs. The class meets twice a week during the daytime plus one weekly evening telescope session, and has a required field trip to Palomar Observatory. Students interested in enrolling should review the logistical information on this page and ensure their schedule allows attendance of all course components prior to registering: https://dekleer.caltech.edu/ayge107. Enrollment is limited.

This course is intended primarily for first-year Ay graduate students, although participation is open and encouraged. Students are required to attend seminar-style lectures given by astrophysics faculty members and other researchers. The intent of the course is for students to gain an understanding of the breadth of astrophysics research that is conducted at Caltech, and to learn about potential research opportunities, as well as different career paths in astronomy. Credit is also given for attending the weekly astronomy colloquia. At the end of each term, students are required to summarize in oral or written form (at the discretion of the instructor), one of the covered subjects that drew their interest. Part c not offered 2026-27.

In modern fields of planetary science and astronomy, vast quantities of data are often available to researchers. The challenge is converting this information into meaningful knowledge about the universe. The primary focus of this course is the development of a broad and general tool set that can be applied to the student's own research. We will use case studies from the astrophysical and planetary science literature as our guide as we learn about common pitfalls, explore strategies for data analysis, understand how to select the best model for the task at hand, and learn the importance of properly quantifying and reporting the level of confidence in one's conclusions.

This class is an introduction to the data science skills from the applied computer science, statistics, and information technology, that are needed for a modern research in any data-intensive field, but with a special focus on the astronomical applications. Open to graduate and upper-division on undergraduate students in all options. The topics covered include best programming practices, supervised and unsupervised machine learning, feature selection, dimensionality reduction, databases, Bayesian statistics, time series analysis, deep learning, data visualization, and possibly other topics. The class will feature real-world examples from cutting-edge projects in which the instructors are involved.

The interaction of radiation with matter: radiative transfer, emission, and absorption. Compton processes, coherent emission processes, synchrotron radiation, collisional excitation, spectroscopy of atoms and molecules.

Measurement and signal analysis techniques throughout the electromagnetic spectrum. Courses may include lab work and field trips to Caltech observatories. Ay 122 a concentrates on infrared, optical, and ultraviolet techniques: telescopes, optics, detectors, photometry, spectroscopy, active/adaptive optics, coronography. Imaging devices and image processing. Ay 122 b concentrates on radio through submillimeter techniques: antennae, receivers, mixers, and amplifiers. Interferometers and aperture synthesis arrays. Signal analysis techniques and probability and statistics, as relevant to astronomical measurement. Ay 122 c concentrates on X-ray through gamma-ray techniques. Part c not offered 2026-27.

Thermodynamics, equation of state, convection, opacity, radiative transfer, stellar atmospheres, nuclear reactions, and stellar models. Evolution of low- and high-mass stars, supernovae, and binary stars.

Stellar dynamics and properties of galaxies; instabilities; spiral and barred galaxies; tidal dynamics and galaxy mergers; stellar composition, masses, kinematics, and structure of galaxies; galactic archeology; galactic star formation; feedback from stars and super-massive black holes; circum-galactic medium.

High-energy astrophysics, the final stages of stellar evolution; supernovae, binary stars, accretion disks, pulsars; extragalactic radio sources; active galactic nuclei; black holes.

Physical processes in the interstellar medium. Ionization, thermal and dynamic balance of interstellar medium, molecular clouds, hydrodynamics, magnetic fields, H II regions, supernova remnants, star formation, global structure of interstellar medium.

Cosmology; extragalactic distance determinations; relativistic cosmological models; thermal history of the universe; nucleosynthesis; microwave background fluctuations; large-scale structure; inter-galactic medium; cosmological tests; galaxy formation and clustering.

Review current theoretical ideas and observations pertaining to the formation and evolution of planetary systems. Topics to be covered include low-mass star formation, the protoplanetary disk, accretion and condensation in the solar nebula, the formation of gas giants, meteorites, the outer solar system, giant impacts, extrasolar planetary systems.

A quantitative review of dynamical processes that characterize long-term evolution of planetary systems. An understanding of orbit-orbit resonances, spin-orbit resonances, secular exchange of angular momentum and the onset of chaos will be developed within the framework of Hamiltonian perturbation theory. Additionally, dissipative effects associated with tidal and planet-disk interactions will be considered.

Oral reports on current research in astronomy, providing students an opportunity for practice in the organization and presentation of technical material. A minimum of two presentations will be expected from each student each year. In addition, students are encouraged to participate in a public-level representation of the same material for posting to an outreach website. This course fulfills the option communication requirement and is required of all astronomy graduate students who have passed their qualifying exam. It is also recommended for astronomy seniors; non-seniors can attend but cannot take the course for credit. Graded pass/fail.

The student should consult a member of the department and have a definite program of research outlined. Approval by the student's adviser must be obtained before registering. 36 units of Ay 142 or Ay 143 required for candidacy for graduate students. Graded pass/fail.

The student should consult a member of the department and have a definite program of reading and independent study outlined. Approval by the student's adviser must be obtained before registering. 36 units of Ay 142 or Ay 143 required for candidacy for graduate students. Graded pass/fail.

This course is intended to be taken by students conducting minor study in the Ay option, subsequent to a term of Ay 142 (Research in Astronomy and Astrophysics), or by students who have completed a SURF with an astronomy faculty member and are writing it up for publication. Students should sign up in the section of the faculty member who supervised the research project. Course requirements are (at minimum) bi-weekly meetings with the research adviser and preparation of a 5-20 page write-up of the work in the style of one of the major journals, such as ApJ/AJ or Science/Nature. This course is required as part of the Ay minor.

This course explores one of the most enduring mysteries in science: the origin of life on Earth and, potentially, beyond. Emphasizing the feedback between laboratory experiments and geochemical evidence, we will examine how natural chemical systems could have given rise to biology with an interdisciplinary approach, spanning prebiotic chemistry, geochemistry, and planetary science. We will investigate early Earth environments alongside the chemistries these settings could have supported. From there, we will discuss key transitions from geochemistry to biochemistry, including the abiotic synthesis of biomolecules, the origin of homochirality, non-enzymatic replication of an early genome, and the emergence of metabolic networks. Extending beyond Earth, we will also explore environments across the solar system, particularly Mars and the icy moons, as well as exoplanetary systems. We will study space missions that constrain plausible abiotic chemistries and consider how these constraints guide the search for life beyond our planet. The course objective is to provide the student with a working framework for understanding life’s emergence based on the available geochemical evidence and laboratory studies.

Introduction to essential numerical analysis and computational methods in astrophysics and astrophysical data analysis. Basic numerical methods and techniques; N-body simulations; fluid dynamics (SPH/grid-based); MHD; radiation transport; reaction networks; data analysis methods; numerical relativity.

Topic for 2026-2027 is Extrasolar Planets. Thousands of planets have been identified in orbit around other stars. Astronomers are now embarking on understanding the statistics of extrasolar planet populations and characterizing individual systems in detail, namely star-planet, planet-planet and planet-disk dynamical interactions, physical parameters of planets and their composition, weather phenomena, etc. Direct and indirect detection techniques are now completing the big picture of extra-solar planetary systems in all of their natural diversity. The seminar-style course will review the state of the art in exoplanet science, take up case studies, detail current and future instrument needs, and anticipate findings.