Reese W. Flower Professor
At Penn since 7/02
4N1 David Rittenhouse Lab
Email: garyb at physics.upenn.edu
209 S 33rd St
Philadelphia, PA 19104
See my list of publications for
more information on these research topics.
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.
||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.
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).
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.
- National Science Foundation
- NASA "Beyond Einstein Foundation Science" program
- Dept. of Energy High Energy Physics program
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 upenn.edu sites)
||Spring 2004: Astronomy 005:
Stars, Galaxies, and the Universe
Software packages of use to the general astronomical community:
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.
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