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Pomona
College Professor Helps Solve 30-Year Space Mystery
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In the 1960’s military satellites discovered incredibly
bright, extremely brief flashes of light originating
somewhere in deep space. While the origin of some gamma ray
bursts was solved in the 1990s, a large group of very short,
hard bursts remained mysterious until now.
 Bryan Penprase, a Pomona College associate professor of
physics and astronomy and director of Pomona’s Brackett
Observatory, is a co-author of an article in the journal
Nature, that solves the question. By locating two short
bursts and combining optical, xray and radio data in new
ways, the research group concluded that the short, hard GRBs
resulted from colliding neutron star that coalesce into a
black hole..
The article is "The Afterglow of GRB050709 and the Nature of
the Short-Hard Gamma-Ray Bursts," Nature, 437, 845-850,
October 6, 2005. The CalTech research team, of which
Penprase is a member, is lead by Shrinivas Kulkarni.
“What makes gamma ray bursts exciting,” explains Penprase,
“is that they have the potential for lighting up parts of
the universe that have never been studied, galaxies from
what is some times called the ‘Cosmic Dark Ages,’ before
more conventional stars formed.”
When stars from distant, primeval galaxies explode, the
burst of light takes an instantaneous snapshot in the same
way that a flashbulb can do of its surroundings.
“Studying GRBs is really the study of the archeology of the
universe by looking at the fossil light that’s traveled
billions of years through space,” says Penprase. “By
studying a few photons that come at us from that early time,
we can exactly watch how things were back then. We’re
looking at galaxies as they actually were in a way that no
other subject allows.”
In addition to direct observation, Penprase is also studying
the spectra of GRBs, a more subtle technique examining the
environment around the GRB. By analyzing GRB spectra
absorption lines, Penprase and the research team can figure
out the different elements and their abundances, their
temperatures and densities and to find out what the galaxies
are like. With Edo Berger, of the Carnegie Observatories of
Pasadena, Penprase is analyzing the light spectra for
GRB50505, one of the earliest and most distant GRB
explosions that has been studied so far.
Student Max Wainwright ’07 has been working with Penprase
and Berber to compile an atlas of space galaxies that host
gamma ray bursts. The project involved using the Hubble
Space Telescope to develop a complete catalog of the
galaxies in which the gamma ray bursts exploded.
One of the main conclusions is that the galaxies seem to
show more asymmetry and departures from their radial
profiles than typical galaxies, which are usually more
quiescent and self-gravitating galaxies. “It’s an amazing
thing he’s pulled off,” says Penprase, who also notes that
Wainwright is the first author on a paper submitted to the
Astrophysical Journal.
Penprase, along with Pomona College Professor Alma Zook and
students Rachel Paterno-Mahler ‘07 and Gordon Stecklein ’08,
with others, was also a co-author of the article “Deep
Impact: Observations from a Worldwide Earth–Based Campaign,”
Science, 14 October 2005. Remotely operating Pomona’s
one-meter telescope on Table Mountain, the Pomona Group
tracked the Deep Impact satellite and comet Tempel 1. On
impact, they took photos every few seconds and compiled a
light curve of the brightening of the comet after impact.
Pomona College, one of the nation’s premier liberal arts
institutions, offers a comprehensive program in the arts,
humanities, social sciences and natural sciences. Its
hallmarks include small classes, close relationships between
students and faculty, and a range of opportunities for
student research. More information about Pomona College can
be found on the Web at www.pomona.edu |
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