We invite you to the public lecture in Astronomical
Institute, Academy of Science of the Czech Republic
Friday November 12, 2004
13:00
in the lecture room in Cosmic Laboratory Ondrejov
Sunspots, Gravitational Redshifts and
Exo-Solar Planet Search
Prof. Jacques Beckers
(National Optical Astronomy Observatory, USA)
I revisit a paper I wrote in 1977 on the spectral line shifts
in sunspot umbra observed on an absolute wavelength scale. In that
paper I examined not only the motions inside sunspots but also the then
already known issues associated
with the "Limb Effect" in the spectrum of the quiet photosphere
(observed in 1907 by Halm). These issues include what is now known as
the "convective blueshift" and the Einstein gravitational redshift. In
sunspots things behave quite differently. In my talk I will compare
sunspot and quiet photosphere spectral line shifts from the modern day
perspective. Although recent
modeling of solar surface convection has resulted in an unambiguous
interpretation of the quiet photosphere line profile and shift
observations, the 1977 paper appears to report the only work done on
the topic in sunspots, both covering observations and interpretation.
The observational technique developed for that research has led
directly to one of the two techniques used by many exosolar "planet
hunters".
Frantisek Farnik
Miroslav Barta
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