The Impact of Star Parallaxes and Very Accurate Proper Motions on Galactic Structure and Dynamics Studies

1980 ◽  
pp. 799-804
Author(s):  
Per Olof Lindblad
1980 ◽  
Vol 5 ◽  
pp. 799-804
Author(s):  
Per Olof Lindblad

Assuming that we have the absolute parallaxes and homogeneous set of proper motions for a large number of stars as described by the previous speakers - how should we use them in studies of galactic structure and dynamics?Concerning the parallaxes I will be very brief - the subject has already been discussed by Dr. Pagel. Clearly, the main importance of the absolute parallaxes obtained is in the calibration of photometric or spectrophotometric absolute magnitude scales. For a sufficient number of stars observed in the Hyades cluster at a distance of 50 pc and in the Scorpius-Centaurus association the systematic error, which lies at the bottom of all subsequent calibration of distance indicators, may be reduced to the same order as the accuracy of photometric measurements.


2013 ◽  
Vol 1830 (10) ◽  
pp. 4974-4980 ◽  
Author(s):  
Daniela Russo ◽  
Maria Grazia Ortore ◽  
Francesco Spinozzi ◽  
Paolo Mariani ◽  
Camille Loupiac ◽  
...  

2022 ◽  
Vol 10 (01) ◽  
pp. 2888-2904
Author(s):  
Dr. MUTESI Jean Claude

The study investigated the socio-economic and environmental impact of hydropower projects in Rwanda with a case study of Rubagabaga hydropower Ltd operating from Nyabihu District. It examines the impact of a socio-economic and environmental hydropower plant in Rwanda, identifies the challenge hydropower plants face in Rwanda, and finally investigates the relationship between hydro powers and their socio-economic impact in Rwanda? In this research, the quantitative research design is based on statistical data of the research that was used with quantitative and qualitative methods. Questionnaires were used to collect data. The target population of this study was made up of 252 participants including 154 respondents all from ten different villages surrounding the Rubagabaga plant in Nyabihu District. Data were analyzed using descriptive and correlation analysis and tables that were interpreted to confirm or deny the relevance of the main and specific objectives. Based on results from table no.16 demonstrates that the beta= 0.397 with the t value of 2.333 and the p-value of 0. 021. Since the p-value is less than 0.05, the researcher rejected the null hypothesis and considered it an alternate. There is a strong positive relationship between environmental assessment of hydropower plant projects and socio-environmental sustenance and development. In a nutshell, the researcher has rejected the null hypothesis and considered its alternate. Community structure and dynamics have a positive influence on socio-environmental sustenance and development. Table no.16 shows that beta= 0.341 with the t value of 2.668 as the p-value was 0.009. Since the p-value is less than 0.05. Therefore, the researcher rejected the null hypothesis and considered it an alternate. According to table no.21, the changes in community structure and dynamics of the hydropower plant project cause the increase of 0.341 (34.1%) of the socio-environment sustenance and development. The ratio of beta modal results for the t value expressed t=2.66 hence the probability value is significant on socio-environment sustenance and development noting that sig. =0.009. Carefully, the researcher has rejected the null hypothesis and considered its alternate. With this in mind, community structure and dynamics has a positive influence on socio-environmental sustenance and development. Table no.16 has shown beta= 0.478 with the t value of 4.543 as the p-value was 0.000 which is less than 0.05. According to the findings, the changes in government policies, stability, and support of hydropower plant project causes the increase of 0.478 (47.80%) of the socio-environment sustenance and development. The ratio of beta modal results for the t value expressed t= 4.54 hence the probability value is significant on socio-environment sustenance and development noting that sig. =0.000.


1999 ◽  
Vol 170 ◽  
pp. 401-409
Author(s):  
David W. Latham

AbstractI review the status of ground-based radial-velocity searches for extrasolar planets and speculate about the new results that can be expected in this field over the coming years. Then I review the plans for astrometric space missions and speculate about the impact that these missions will have on ground-based radial-velocity work, citing the specific examples of extra-solar planet research, the mass-luminosity relation for M dwarfs and metal-poor stars, and Galactic structure and evolution.


1974 ◽  
Vol 61 ◽  
pp. 217-220
Author(s):  
S. V. M. Clube

A method of analysing proper motions as observed over all the sky is described. The kinematics of nearby stars derived from the Lick Pilot Survey are discussed, and the consequences to galactic structure examined.


1995 ◽  
Vol 148 ◽  
pp. 208-217
Author(s):  
Neill Reid

AbstractPhotographic plates are well established as stable detectors, well suited for positional astronomy. The completion of the current second epoch 48 inch Schmidt surveys in both hemispheres will provide material spanning baselines of 20–45 years, allowing proper motions to be determined to an accuracy of 4–7 mas yr−1. This paper discusses some of the Galactic structure problems that these data, combined with accurate photometry, can be used to address.


1998 ◽  
Vol 179 ◽  
pp. 228-230
Author(s):  
A. Spagna ◽  
M.G. Lattanzi ◽  
G. Massone ◽  
B.J. McLean ◽  
B.M. Lasker

Faint surveys of accurate colors and proper motions are fundamental for studying the physical and kinematical properties of the stellar populations in the Galaxy. A program designed to address such issues has been initiated on selected fields utilizing prototype material from the GSC-II project (see McLean et al. in this volume, p. 431). Photographic photometry V, B–V, V–Rc, is derived down to V = 18.5 with a precision of about 0.1 mag, together with absolute proper motions to σμ ≃ 3 mas/yr.


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