Department of Astrophysical Sciences

Exploration of the large-scale universe around us, including the planets, the sun, other stars, galaxies, clusters and superclusters of galaxies, quasars, and the background radiation field is the object of modern astronomy. Observations needed for probing the universe are made mostly with telescopes, not only the familiar ones sensitive to optical light rays, but also with instruments designed to receive radio waves, X rays, and gamma rays. Within the solar system, astronomers use space probes. The vast amount of observational detail obtained with these techniques is then interpreted by means of the basic laws of physics.

Especially in recent decades, the new tools of radio telescopes on the ground and X-ray and ultraviolet telescopes in space have permitted us to make startling discoveries about the heavens. For example, we now know dense stars consist almost entirely of neutrons, with the same amount of material as in the sun compressed into a sphere only a few miles in diameter, with a resultant density of millions of tons packed into each cubic inch. There is evidence that even smaller, more massive objects have been found whose gravitational attraction is so great that any light waves from the surface cannot escape but are attracted back. Such objects are called “black holes.” Gigantic explosions within individual galaxies have been found to radiate as much light as billions of suns. Such explosions have been detected in systems as far out as the edge of the accessible universe, where stellar systems are moving away from us at more than four-fifths the speed of light and from which the light rays we now see were emitted billions of years ago when the universe was much younger.

While such discoveries are fascinating in their own right, they cast light on fundamental questions that people have been asking since the dawn of humankind. How did the universe start? What is its fate? What part do the earth and life on it play in this cosmic drama? Frequently the study of abstract astronomical problems has yielded information of practical importance. For example, the study of motion of ionized gases in the magnetic fields of stars and interstellar space has yielded methods for confining hot gases on the earth and may make possible a virtually inexhaustible reservoir of hydrogen fusion for practical power generation.

The undergraduate program in astronomy is relatively small, usually about 10 students each year. For those who are fascinated by the prospect of contributing to the search for the universe’s hidden secrets, the rewards of studying astronomy, in terms of intellectually significant work, can be great.

Our program consists of two components, coursework and independent research projects under the close supervision of a faculty member. The coursework is designed to give a solid background in the relevant areas of astronomy, physics, and math. We place a particularly strong emphasis on the independent research component, which allows students to carry out real “frontier” research in astronomy and to gain a working experience of what it is like to do professional astronomical research. A measure of our success is that a substantial fraction of our graduating seniors have cowritten one or more papers published in the astronomical literature as a result of their junior paper or senior thesis work. Another measure of our program’s overall effectiveness and, perhaps more importantly, of the quality of the students at Princeton, is the remarkable success our students have achieved in their graduate school applications. Typical recent graduating classes sent students to Berkeley, Caltech, Harvard, and Stanford and included winners of various fellowships and awards. Needless to say, our program is a rigorous one, intended to challenge and serve the first-class students that Princeton regularly attracts. In addition to the scientific excellence of the department, its relatively small size allows for an informal atmosphere and a highly accessible faculty, both of which are greatly enjoyed by our majors.

The astrophysics program is flexible and accommodates students with a broad range of interests. While many of our students plan to continue in graduate school in astrophysics, we offer a flexible choice of courses and research projects for students with other career goals, in areas such as science education, science policy, and space exploration, as well as law, medicine, finance, and teaching.

Princeton has a 3.5-meter telescope in Sunspot, New Mexico. The telescope is operable remotely from Princeton, and undergraduate majors have the opportunity to collaborate with faculty on research projects using the telescope. Princeton is also part of the Sloan Digital Sky Survey, a multi-institution collaboration to map the universe in three dimensions by obtaining redshifts of one million galaxies. Data from the Sloan survey have recently discovered the most distant quasars in the universe and the coolest known stars. Undergraduate majors are collaborating on the scientific analysis from this unique and most exciting survey. Research opportunities during the academic year, as well as in the summer, are available for potential astrophysics majors. Details and requirements of the program are available on the Web at www.astro.princeton.edu under the undergraduate program.