The impact of Hipparcos on our knowledge of nearby stars


Hartmut Jahreiß, Roland Wielen, Burkhard Fuchs, Heidelberg



The astrometric satellite Hipparcos observed almost 90 % of the presently known nearby stars in the magnitude range accessible by the satellite. It detected almost 200 new nearby objects, the nearest one at 5.4 pc, and 39 new components. Consequently, the new version of the Catalogue of Nearby Stars (CNS4), which was compiled on the basis of the Hipparcos measurements, achieved an unprecedent quality.

Compared with the last ground-based version (CNS3) the number of stars within the chosen distance limit of 25 pc remained more or less the same. But, a considerable shift to larger distances took place, so, that a high portion of stars formerly included due to large and rather poor trigonometric parallaxes could now be removed, unequivocally.

The bright part (absolute V-magnitude brighter than 9 mag) of the new nearby star sample is complete within a much larger volume than before. In other words, Hipparcos cleaned up the bright portion of the Colour-Magnitude diagram, which represents now the true distribution of the massive stars within 25 pc and allows more precise studies of kinematics, metallicity and age effects.

Likewise, the bright end of local stellar luminosity function could be determined with higher accuracy than before: the result is a 15 per cent decrease in star number density, and in a slightly lower stellar mass density of 0.039 solar masses per cubic parsec.

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Bibliographical details:

Hartmut Jahreiß, Roland Wielen, Burkhard Fuchs: The impact of Hipparcos on our knowledge of nearby stars. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae ; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. 171-180.