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Observational Facilities

The department is a member of the Associated Universities for Research in Astronomy (AURA), and the Astrophysical Research Consortium (ARC). ARC operates two major facilities at Apache Point Observatory in Southern New Mexico:

  •  A 3.5-meter optical telescope in which Princeton has a 16% share. This is a standard optical    telescope,with instrumentation for imaging and spectroscopy in visible and near-infrared wavelengths.  Princeton researchers have used this telescope to make the first definitive measurement of time delay in a gravitationally lensed quasar, to follow-up the discovery of the first supernova explosion seen in X-rays, and to follow up discoveries of high-redshift quasars and brown dwarfs with the Sloan Digital Sky Survey.
  •  A 2.5-meter optical telescope, dedicated to wide-field surveys of the sky.  Princeton University has played a leadership role in the Sloan Digital Sky Survey (SDSS).  It has completed an eight-year survey of the sky, resulting in a dataset that has been used in over 2500 scientific papers.  It has been called the most scientifically productive observatory in several recent years (as indicated by rank and productivity studies).  20 of the 100 most cited refereed papers in astrophysics in the last decade have been based at least in part on data from SDSS, and its discoveries range from the most distant quasars, to precise measurements of the clustering of galaxies, to structure in the halo of the Milky Way.

The SDSS has started a new phase  to last through 2014, with three major scientific themes:

  • A redshift survey of galaxies to z~0.7, and quasars to z~3.0, to   study baryon oscillations in the clustering signal at high   redshift;
  • Spectroscopic studies of stellar populations in the Milky Way,   both at moderate dispersion (R=2000) in the optical, and high   dispersion (R~20,000) in the near-infrared;
  •  A radial velocity search for planets.


An imaging survey to search for planets and debris disk around other stars, the Subaru Strategic Exploration of Exoplanets and Disk Survey (SEEDS), a collaboration between Japanese and Princeton astronomers, uses adaptive optics and a coronagraph on the Subaru 8.2-meter telescope; it has recently started taking data, and has been allocated 120 nights of telescope time over the next five years.

Since the Subaru 8.2-meter telescope has the widest field of view of any telescope in its size class, it is ideal for wide imaging and spectroscopic  surveys of the sky.  Working with our Japanese colleagues, we are launching the SUbaru Measurements of Images and REdshifts (SUMIRE) program.  The first step in this project, Hyper-SuprimeCam is currently under construction and  will have a field of view of 1.77 square degrees. We are currently planning a series of nested imaging surveys at different depths.  The next step in the program will be  a wide field Prime Focus multi-object Spectrograph (PFS) that will be capable of spectroscopic follow-up on many of the imaged galaxies.


We have played a major role in the building of the Wilkinson Microwave Anisotropy Probe (WMAP) and the analysis of its data, resulting in the three most cited refereed papers in astrophysics in the last decade.  These data measuring fluctuations in the Cosmic Microwave Background have firmly established what is now the standard cosmological model, and allow a determination of the age, composition, structure, and geometry of theuniverse to exquisite precision.

We are carrying out a ground-based experiment, the Atacama Cosmology Telescope (ACT) to measure the fluctuations in the CMB on smaller angular scales, which will enable further cosmological probes and explore the physics of the interaction of CMB photons with matter in the relatively nearby universe.