Astrometric angles
نویسندگان
چکیده
منابع مشابه
Astrometric surveys
Astrometric surveys are a basic tool for galactic astronomy: they provide the only distance determination without assumption about the observed object as well as two components of the space velocity. A large number of stars, observed in a systematic way, yield to an unbiased sampling of the Galaxy and, for the most accurate surveys, of the brightest parts of Local Group galaxies, at larger and ...
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There are at least four unexplained anomalies connected with astrometric data. Perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass. Next, a secular change in the astronomical unit AU is definitely a concern. It is increasing by about 15 cm yr−1. The o...
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New memberships, mean parallaxes and proper motions of all 9 open clusters closer than 300 pc (except the Hyades) and 9 rich clusters between 300 and 500 pc have been computed using Hipparcos data. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to 0.5 mas/yr for proper motions, are of great interest for calibrating photometric parallaxes as well as for kinematical studies. Caref...
متن کاملAstrometric Microlensing of Stars
Due to dramatic improvements in the precision of astrometric measurements, the observation of light centroid shifts in observed stars due to intervening massive compact objects (‘astrometric microlensing’) will become possible in the near future. Upcoming space missions, such as SIM and GAIA, will provide measurements with an accuracy of 4–60 μas depending on the magnitude of the observed stars...
متن کاملAstrometric Effects of Secular Aberration
One of the main endeavors of fundamental astrometry is to establish a practical realization of a non-rotating, inertial reference frame anchored to celestial objects whose positions are defined in the barycentric coordinates of the solar system matching the current level of astrometric observational accuracy. The development of astrometric facilities operating from space at a microarcsecond lev...
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ژورنال
عنوان ژورنال: Nature
سال: 1986
ISSN: 0028-0836,1476-4687
DOI: 10.1038/319824a0