Gary Bernstein
Reese W. Flower Professor

At Penn since 7/02

Phone: (215)-573-6252
Fax:      (215)-898-2010

4N1 David Rittenhouse Lab
209 S 33rd St
Philadelphia, PA 19104

Email: garyb at
Research Courses Publications Family
Software Pictures Links CV

Research Projects

See my list of publications for more information on these research topics.
Weak Gravitational Lensing: The dark matter in the Universe reveals its presence by its gravitational deflection of passing light rays. This causes very subtle distortions in the appearance of background galaxies, which can be used to unveil the structure of this dark matter. We have used this weak gravitational lensing effect to measure the mass of dark matter halos around typical galaxies, and the power spectrum of matter in the Universe. We have also worked extensively on methods to produce the best possible lensing results from future surveys, which will allow us to track the evolution of dark matter in the Universe. Here's a summary talk (19 MB) about weak lensing presented (not very recently!) at SLAC.
The Kuiper Belt: There are many thousands of small icy bodies orbiting the Sun beyond Neptune, remnants of the early phases of the formation of our Solar System. These Kuiper Belt Objects (KBOs) contain many clues to the early steps of planet formation. We have worked from the ground to discover many of these KBOs, confirming that very few exist beyond Pluto's orbit. Using the Hubble Space Telescope we have found the faintest Solar System objects ever discovered - but not enough of them! There are surprisingly few small Kuiper Belt Objects.
SNAP: The SuperNova Acceleration Probe is a planned wide-field imaging space telescope for measuring distant supernovae and gravitational lensing. Both measurements will be focussed on measuring the evolution of the dark matter and dark energy components of the Universe, which remain totally unexplained despite being the dominant contents of the Universe. I am a member of the SNAP collaboration, working on calculation and optimization of its imaging and spectroscopic capabilities (e.g. the ETC++ exposure-time calculator).
LSST: The Large Synoptic Survey Telescope is a proposed 8-meter ground-based telescope capable of imaging the entire accessible sky every 4 days. It would be extraordinarily capable for locating near-Earth asteroids, Kuiper Belt objects, nearby supernovae, large-scale gravitational lensing, and many other phenomena. I was a member of the Science Working Group for LSST.
Support: These investigations are supported by the following programs. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or other funding agencies.

Astronomical Pictures

Here are some pretty astronomical images produced from our data over the past few years. Copyright is maintained by the University of Michigan and/or Lucent Technologies. Reproduction or commercial use of these images requires my permission. High-resolution versions of these images are available upon request.

Reflection Nebula in Orion (83 kB)
The Tarantula Nebula (270 kB)
The Kuiper Belt Movie


Courses taught at the University of Pennsylvania:

Spring 2004, 2006: Astronomy 503: Astronomical Methods and Instrumentation. This is the website for the programming-techniques version of the course. You can find lecture notes for the instrumentation version of the course here.
Fall 2006: Astronomy 003: The Solar System (lecture materials available here for viewers at sites)
Spring 2004: Astronomy 005: Stars, Galaxies, and the Universe


Software packages of use to the general astronomical community:
Orbit-fitting software as described in Bernstein & Khushalani (2000). Version 2.0 of this code available here,. Also requires C programs to work with DE405 Ephemeris. Observations of outer Solar System objects can be fit, and sensible uncertainties can be placed on orbital elements and predicted positions even in the case of degenerate orbit fits.
Rigorous coupled-wave solutions for volume phase holographic (VPH) gratings. Software and documentation are here. Also will require the Meschach linear algebra library.
ETC++ advanced exposure-time calculations as described in Bernstein (2002). Software available here. Unlike most exposure-time calculators, this one can consider the effect of cosmic rays, undersampling, dithering, and imperfect pixel response functions. Errors on astrometry and galaxy shape measurements can be predicted as well as photometric errors.

Last modified 9/30/08 by gmb