Research

The primary mission of our department is twofold: the performance of cutting-edge research in astronomy and astrophysics, including theory, observation, and experiment, as well as the education of undergraduate and graduate students and training of postdoctoral research associates who will comprise the scientists and leaders of tomorrow.

Caltech is one of the world's preeminent centers of astronomical research. This is due to the combination of excellent human resources with premier observational facilities and computational infrastructure. Fundamental discoveries in astronomy and astrophysics are a part of Caltech's past, present, and future.

Students from either the astronomy or the physics options are best prepared to undertake research with faculty in the Cahill Center for Astronomy and Astrophysics. Students from related options such as planetary science, computer science, applied physics, and electrical engineering are also welcome.

Areas of Research

Astronomy and astrophysics are synonymous at Caltech. Caltech scientists and students are involved in many frontier areas of research, and have been known to open new ones. Research techniques include observations, theory, numerical simulation, advanced data analysis, laboratory astrophysics, and detector development. Projects and groups often bridge these areas of inquiry.

Topics of current research interest include: observational cosmology and the nature of dark matter and dark energy; studies of the cosmic microwave background; galaxy formation and evolution; quasars and other active galactic nuclei and radio sources; studies of the dynamics and com- position of galaxies and clusters; physics and evolution of the intergalactic medium; interstellar matter; local star and planet formation; extrasolar planetary systems; the structure of the galaxy; globular clusters; stellar abundances; supernovae, gamma-ray bursts, and other types of cosmic explosions and transient phenomena; neutron stars and black holes; accretion disks; digital sky surveys and astroinformatics; numerical general relativity; gravitational wave astronomy and many others.

Research in planetary and solar system astronomy is often pursued in cooperation with groups in the Division of Geological and Planetary Sciences. New types of astronomical detectors and satellites, that can revolutionize various areas of astronomical research, are developed with groups in physics and colleagues at JPL.

In addition to maintaining a leading numerical general relativity group, Caltech theorists also use high-performance computing facilities for simulations of supernova explosions, merging black holes, cosmic structure formation, etc. Caltech is leading the development of novel tools for knowledge discovery in massive and complex astronomical data sets, many obtained with Caltech facilities.

History and Current Science at Observational Facilities

Observational astronomy is pursued both from the ground-based sites and from space-based platforms. Caltech operates, or has access to an unprecedented, comprehensive set of observational facilities, spanning the entire electromagnetic spectrum. Caltech is also playing a key role in opening a new window on the universe, the gravitational wave sky.

Historically, Caltech's pioneering role in astronomy started with Palomar Observatory (about 190 km from campus), funded by the Rockefeller Foundation. The first telescope on the mountain was an 18-inch Schmidt telescope built by Fritz Zwicky and used to conduct pioneering sky surveys for supernovae, potential planetary hazard asteroids, etc. The 200-inch Hale Telescope, constructed through the 1930s and 1940s, has been used to make many historical, fundamental discoveries ever since its commissioning in 1948, including the dis- covery of quasars, and many studies of stellar populations, galaxies, intergalactic medium, etc., and it continues to produce excellent sci- ence. Novel detectors and instruments were developed there, e.g., the first astronomical CCDs and infrared detectors as well as pioneering advances in adaptive optics in addition to optical and infrared spec- troscopy. The 48-inch Samuel Oschin Telescope has made possible complete surveys of the northern sky, initially with photographic plates (including the historic POSS-I and POSS-II surveys), and now with large-format CCD array cameras. It is currently operating a uniquely wide field, high-cadence program, the Zwicky Transient Facility (ZTF).

A much larger camera for this telescope, with a 47-square-degree field, started operation in 2018, as the Zwicky Transient Facility (ZTF). The 60-inch telescope has been roboticized, and is used to monitor sources discovered by sky surveys.

In the 1990s, funded mainly by the Keck Foundation, Caltech and University of California constructed two 10-m telescopes on Mauna Kea, Hawaii. The W. M. Keck Observatory produced many recent dis- coveries in the fields of galaxy formation and evolution, intergalactic medium, extrasolar planets, cosmic gamma-ray bursts, etc. Caltech is a founding partner in the development of the Thirty-Meter Telescope (TMT), the first of the next generation of extremely large optical/infrared telescopes.

At meter to centimeter wavelengths, Caltech operates the Owens Valley Radio Observatory (OVRO) in a radio-quiet location about 400 km from Pasadena, near Big Pine, California. Its facilities include a 40-meter telescope, a growing 288 element long wavelength array which can image the entire sky every second, and a 6.1 meter tele- scope dedicated to observations of polarized radio emission from the galaxy. New radio and submm telescopes are in design and con- struction phases. From the 1980s until 2015, Caltech also operated the Caltech 10-m Submillimeter Observatory (CSO) on Mauna Kea in Hawaii, and a series of millimeter interferometers, culminating in the 23-antenna Combined Array for Research in Millimeter-wave Astronomy (CARMA) in the Inyo Mountains. These telescopes, currently being repurposed to new experiments, pioneered submm imaging and inter- ferometry and mm wave interferometry, now carried out by the interna- tional Atacama Large Millimeter/submm Array (ALMA).

In Antarctica, Caltech's BICEP2 telescope, which measures the imprint of inflation's gravitational waves on the COSMIC microwave background, has been expanded and renamed the Keck Array.

On the space observations front, Caltech hosts NASA's Spitzer Science Center (SSC) and IPAC, which are principal national archives for astronomy. Caltech scientists lead or actively participate in a num- ber of astrophysics missions, currently including the Spitzer Space Telescope, and the NuSTAR hard X-ray mission. Caltech and the Jet Propulsion Laboratory (JPL) are also leading the development of the forthcoming SPHEREx mission, that will study the early stages of the universe, galaxy formation, and formation of planetary systems. There are numerous close connections with JPL, that designs and operates a number of NASA's scientific missions. Finally, Caltech astronomers are major users of NASA's astronomical satellites, the Hubble Space Telescope, Chandra, Fermi, Herschel, Planck, etc., ALMA and the NSF's Jansky Very Large Array (JVLA).

Caltech is the headquarters for LIGO lab, which built and operates the world's most sensitive gravitational wave observatory, the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO), which in 2015 made the historic first detection of gravitational waves from a black hole binary. Several other black hole mergers have been detected since then, as well as the first gravitational wave detection of a merger of two neutron starts in 2017. Numerous other discoveries are expected as the operations continue.