DTIC ADA521861: Astrometric Jitter of the Sun pdf

DTIC ADA521861: Astrometric Jitter of the Sun

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The daily variation of the solar photocenter over some 11 years is derived from the Mount Wilson data reprocessed by Ulrich et al. 2010 to closely match the surface distribution of solar irradiance. The standard deviations of astrometric jitter are 0.52 microAU and 0.39 microAU in the equatorial and the axial dimensions, respectively. The overall dispersion is strongly correlated with the solar cycle, reaching 0.91 microAU at the maximum activity in 2000. The largest short-term deviations from the running average (up to 2.6 microAU) occur when a group of large spots happen to lie on one side with respect to the center of the disk. The amplitude spectrum of the photocenter variations never exceeds 0.033 microAU for the range of periods 0.6-1.4 yr, corresponding to the orbital periods of planets in the habitable zone. Astrometric detection of Earth-like planets around stars as quiet as the Sun is not affected by star spot noise, but the prospects for more active stars may be limited to giant planets

• Creator/s: Defense Technical Information Center
• Date: 5/1/2010
• Year: 2010
• Book Topics/Themes: DTIC Archive, , CALIFORNIA UNIV LOS ANGELES DEPT OF PHYSICS AND ASTRONOMY, *SUN, *JITTER, SUNSPOTS, PERIODIC VARIATIONS

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