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The colloquium is held
at Melamed Hall (Room 6) in the Shenkar Physics
Building, every Sunday at 16:10. Light refreshments
are served outside Melamed Hall at 15:50.
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Sunday, 25 March 2001,
16:00
Gerson Goldhaber
U of CA in
Berkeley and Lawrence Berkeley National Lab (LBNL)
"Evidence
for Dark Energy from a Study of Supernovae"
Abstract
Type
Ia supernovae have been observed to be very good "Standard Candles"
after suitable calibration. In the Supernova Cosmology Project we have
observed over 100 such distant supernovae with redshifts between 0.18 and
1.2. In a study of
42
of these supernovae and comparison with 18 "near by" supernovae we have
obtained evidence for a cosmological constant or perhaps some other form
of "Dark Energy". I will also present preliminary results on a number of
SNe observed with the Hubble Space telescope. This implies that at the
present epoch the expansion of the universe is accelerating. Our data are
strongly inconsistent with the previously preferred cosmology with OMEGA_m
= 1. We also give a direct proof that the red-shift is due to the expansion
of the universe rather than some other process, such as "tired light".
I will also briefly
describe
the plans of the SNAP collaboration to design, build and launch a satellite.
Highlights are a 2 meter mirror and a one square degree field of view involving
about 150 high resistivity CCD's and 3 spectrometers covering the region
from UV to near-IR. The aim is to discover and completely measure 2000
SNe per year with redshifts from 0.1 to 1.7 all with tightly controlled
systematics. In particular SNAP will allow us to explore possible effects
due to "grey" dust and/or evolution on our measurements.
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For
more information or for directions to Melamed Hall please contact: Yardena
Mori +972-3-640-8636
To
suggest potential speakers or register feedback contact: David
J. Bergman +972-3-640-8543
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Tel
Aviv University