Astronomy and Astrophysics – Astrophysics – Instrumentation and Methods for Astrophysics
Scientific paper
2011-12-26
Astronomy and Astrophysics
Astrophysics
Instrumentation and Methods for Astrophysics
PhD thesis of University of Nice-Sophia Antipolis, Sapienza University of Rome and French-Italian University; 109 pages with c
Scientific paper
The measurement of the solar diameter is introduced in the wider framework of solar variability, and, consequently of the influences of the Sun upon the Earth's climate. It is possible to measure the solar diameter with enough accuracy to study climate changes and irradiation variations using ancient eclipses. This would permit to extend the knowledge of the solar luminosity back to three centuries, through the parameter W=dLogL/dLog R. The method of eclipses and Baily beads is discussed, and a significant improvement with respect to the last 40 years, has been obtained by reconstructing the Limb Darkening Function from the Baily's bead light curve, and the search of its inflexion point. The case of the Jan 15, 2010 annular eclipse has been studied in detail, while the atlas of Baily's beads with worldwide contributions by IOTA members, along with the solar diameter during the eclipse of 2006, have been published. The transition between the photographic atlas of the lunar limb (Watts, 1963) and the laser-altimeter map made by the Kaguya lunar probe and published in November 2009 has been followed. The other method for the accurate measurement of the solar diameter alternative to the Picard / Picard-sol mission is the drift-scan method used either by the solar astrolabes either by larger telescopes. The observatories of Locarno and Paris have started an observational program of the Sun with this method with encouraging results. For the first time an image motion of the whole Sun has been detected over frequencies of 1/100 Hz. This may start explain the puzzling results of the observational campaigns made in Greenwich and Rome from 1850 to 1955. A giant pinhole telescope as the meridian line of Santa Maria degli Angeli in Rome, permits to introduce almost all the arguments of classical astrometry presented in this thesis. In this consists the final didactic outreach.
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