scholarly journals The Open Cluster M67 as a Fundamental Standard of Reference for Stellar Properties

1985 ◽  
Vol 111 ◽  
pp. 361-364
Author(s):  
Kenneth Janes
Keyword(s):  
Open Cluster ◽  
Accurate Determination ◽  
Distance Modulus ◽  
The Sun ◽  
Distance Measurements ◽  
Photoelectric Photometry ◽  
Sources Of Error ◽  
Motion Studies ◽  
Stellar Properties

With the possible exception of the Hyades, M67 is the best-studied star cluster. Accurate photoelectric photometry exists well down onto the main sequence and proper motion studies have isolated cluster stars from the field. From photometry and spectroscopy, its composition is determined to be almost exactly the same as the Sun, with an age about one-half billion years less. This similarity to the Sun permits an accurate determination of distance to M67 independently of other distance measurements. Using the Sun as a reference, the distance modulus of M67 is found to be 9.48 mag. An extensive analysis of possible sources of error leads to an uncertainty (standard error) of ± 0.15 mag., with the chief sources of error being the color index of the Sun, the composition of the cluster, and its age. The M67 distance uncertainty compares favorably with Hanson's (1975) Hyades modulus of 3.29 ± 0.08.

scholarly journals Microarcsec Astrometry: The Gaia Mission

1998 ◽  
Vol 11 (1) ◽  
pp. 581-582
Author(s):  
L. Lindegren ◽  
M.A.C. Perryman
Keyword(s):  
Accurate Determination ◽  
Distance Measurements ◽  
Profound Impact ◽  
Individual Stars ◽  
The Galaxy ◽  
Direct Distance ◽  
Scientific Potential ◽  
Space Astrometry ◽  
Small Instrument

The Hipparcos mission demonstrated the efficiency of space astrometry (in terms of number of objects, accuracy, and uniformity of results) and the fact that a relatively small instrument can have a very large scientific potential in the area of astrometry. However, Hipparcos could probe less than 0.1 per cent of the volume of the Galaxy by direct distance measurements. Using a larger instrument and more efficient detectors, it is now technically feasible to increase the efficiency of a space astrometry mission by several orders of magnitude, thus encompassing a large part of the Galaxy within its horizon for accurate determination of parallaxes and transverse velocities. Such a mission will have immediate and profound impact in the areas of the physics and evolution of individual stars and of the Galaxy as a whole.

Introductory remarks

1978 ◽  
Vol 284 (999) ◽  
pp. 1-2
Keyword(s):  
Great Barrier Reef ◽  
Royal Society ◽  
Accurate Determination ◽  
The Sun ◽  
Barrier Reef ◽  
The South ◽  
The Face ◽  
The Universe ◽  
Do So

What we are here to discuss concerns the Great Barrier Reef of Australia. It is very fitting that we should do so in this place, because the Royal Society was intimately concerned with events that led to its discovery in 1770. We go back to 1716, to a communication printed in Latin in the Philosophical Transactions by Edmond Halley, then Savilean Professor of Geometry at Oxford and Secretary of this Society. There, and for no less an objective than the more accurate determination of the dimensions of the Universe, he drew attention to the unique opportunities to that end to be presented by observing the transits of Venus across the face of the Sun due on 6 June 1761 and 3 June 1769. In the event international observations in the former year were largely fruitless, giving added reason for adequate observations in 1769. One of the conclusions of the specially appointed Transit Committee of the Society was that one site for observation should be in the South Seas.

scholarly journals A New Survey of Globular Cluster Structural and Luminosity Parameters

1988 ◽  
Vol 126 ◽  
pp. 489-490
Author(s):  
B. Cameron Reed ◽  
Charles J. Peterson
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Structural Parameters ◽  
Accurate Determination ◽  
Simplex Algorithm ◽  
Photoelectric Photometry ◽  
Central Surface ◽  
The Galaxy ◽  
Photometric Measurements

We have made an analysis of the visual photometric data contained in the Catalogue of Concentric Aperture UBVRI Photoelectric Photometry of Globular Clusters (Peterson 1986). Structural parameters have been obtained by use of the Simplex algorithm of Caceci and Cacheris (1984) to fit the model curves of King (1966) to the run of cluster luminosity with radius. We find that concentric aperture photometry alone can be used to determine globular cluster core radii and central surface brigtnesses reliably. Application of this techique, however, is limited to about two-thirds of the known clusters of the Galaxy because no or inadequate numbers of photometric measurements exist for the remaining clusters. Accurate determination of cluster concentration classes still requires use of other types of data, such as star counts.

XII.—On an Electrically Controlled Thermostat and other Apparatus for the Accurate Determination of the Electrolytic Conductivity of Highly Conducting Solutions

1910 ◽  
Vol 30 ◽  
pp. 254-264
Author(s):  
John Gibson ◽  
G. E. Gibson
Keyword(s):  
Accurate Determination ◽  
Maximum Error ◽  
Electrolytic Conductivity ◽  
Inorganic Salts ◽  
Heating Effect ◽  
Dilute Solutions ◽  
Concentrated Solutions ◽  
Temperature Variations ◽  
Sources Of Error

Kohlrausch and others have recently published investigations which show that the electrolytic conductivity of dilute solutions of inorganic salts may be determined with a maximum error of two or three in ten thousand.Hitherto such accuracy has not been attained with highly conducting concentrated solutions. With such solutions different difficulties are encountered from those met with in dilute solutions. Temperature variations originating outside the cell, the heating effect of the current within the cell, and polarisation are sources of error which are particularly troublesome in the case of highly conducting solutions.

scholarly journals VLBI Observations of Turbulence in the Inner Solar Wind

1996 ◽  
Vol 154 ◽  
pp. 65-75
Author(s):  
Steven R. Spangler
Keyword(s):  
Solar Wind ◽  
Accurate Determination ◽  
The Sun ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Outer Corona ◽  
Very Long Baseline Array ◽  
Made In

AbstractI discuss the use of Very Long Baseline Interferometer (VLBI) phase scintillations to probe the conditions of plasma turbulence in the solar wind. Specific results from 5.0 and 8.4 GHz observations with the Very Long Baseline Array (VLBA) are shown. There are several advantages of phase scintillation measurements. They are sensitive to fluctuations on scales of hundreds to thousands of kilometers, much larger than those probed by IPS intensity scintillations. In addition, with the frequency versatility of the VLBA one can measure turbulence from the outer corona ~ 5 –10 R⊙ to well past the perihelion approach of the Helios spacecraft. This permits tests of the consistency of radio propagation and direct in-situ measurements of turbulence. Such a comparison is made in the present paper. Special attention is dedicated to measuring the dependence of the normalization coefficient of the density power spectrum, on distance from the sun. Our results are consistent with the contention published several years ago by Aaron Roberts, that there is insufficient turbulence close to the sun to account for the heating and acceleration of the solar wind. In addition, an accurate determination of the relationship could aid the detection of transients in the solar wind.

Places of formation of young and moderately young stars

1967 ◽  
Vol 31 ◽  
pp. 323-329 ◽  
Author(s):  
Bengt Strömgren
Keyword(s):  
Spiral Structure ◽  
Narrow Band ◽  
Accurate Determination ◽  
Young Stars ◽  
Photoelectric Photometry ◽  
Peculiar Velocities ◽  
Stellar Ages ◽  
The Galaxy ◽  
Perseus Arm

Narrow-band photoelectric photometry can furnish classification indices allowing accurate determination of stellar ages. From these ages, together with well-determined space motions, the places of formation of stars, and their relationship to the spiral structure of the Galaxy, may be determined. This procedure has been successfully followed for 52 B8–B9 stars within 200 pc from the Sun. It turns out that seven of these have originated in the Perseus Arm, with local peculiar velocities of about 22 km/sec.A simple model is developed describing places of star formation in the Perseus Arm and velocities at formation. The distribution of space velocities and of ages for stars formed according to this model appears to be in agreement with observation.

Introductory remarks

1978 ◽  
Vol 291 (1378) ◽  
pp. 3-4
Keyword(s):  
Royal Society ◽  
Accurate Determination ◽  
The Sun ◽  
Barrier Reef ◽  
James Cook ◽  
The Face ◽  
George Iii ◽  
The Universe ◽  
Do So

What we are here to discuss concerns the Great Barrier Reef of Australia. It is very fitting that we should do so in this place, because the Royal Society was intimately concerned with events that led to its discovery in 1770. We go back to 1716, to a communication printed in Latin in the Philosophical Transactions by Edmond Halley, then Savilean Professor of Geometry at Oxford and Secretary of this Society. There, and for no less an objective than the more accurate determination of the dimensions of the Universe, he drew attention to the unique opportunities to that end to be presented by observing the transits of Venus across the face of the Sun due on 6 June 1761 and 3 June 1769. In the event international observations in the former year were largely fruitless, giving added reason for adequate observations in 1769. One of the conclusions of the specially appointed Transit Committee of the Society was that one site for observation should be in the South Seas. A direct appeal to George III produced one of the earliest grants of money for purely scientific purposes, and even more to the point the Admiralty was in almost enthusiastic agreement. Sweeping aside the Committee’s proposal that Dalrymple should head the expedition, the Admiralty selected Mr James Cook, previously surveyor of the lower reaches of the St Lawrence and of the coasts of Newfoundland. He was now commissioned Lieutenant of H. M. S. Endeavour , and the transit was to be observed from the island of Tahiti recently discovered by Wallis on H. M. S. Dolphin .

scholarly journals A Response to the Response

1999 ◽  
Vol 7 (1) ◽  
pp. 13-13
Author(s):  
Barry R. J Rittman
Keyword(s):  
Image Analysis ◽  
Quantitative Data ◽  
Accurate Determination ◽  
Previous Article ◽  
Relative Importance ◽  
Section Thickness ◽  
Sources Of Error ◽  
Potential Sources

The purpose of my previous article was to identify many of the potential sources of error to be considered when evaluating quantitative data from immunohistochemistry (IHC) and histochemical reactions on sections.Factors that may affect the evaluation of quantitative IHC data were listed but not necessarily placed in their order or importance. This would be difficult to do, as the relative importance of factors may differ for different antigens and histochemical procedures.As far as can be determined, there appear to be no definitive articles that unequivocally show that IHC reactions are stoichiometric. In most laboratories, it is impractical to accurately determine section thickness, and furthermore many of the image analysis systems used may be somewhat rudimentary. Accurate determination of section thickness may therefore be somewhat of a moot point.

scholarly journals White Dwarf Probes of Interstellar Deuterium

2000 ◽  
Vol 198 ◽  
pp. 485-486
Author(s):  
Wayne Landsman
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
White Dwarf ◽  
White Dwarfs ◽  
Accurate Determination ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Space Telescope ◽  
Imaging Spectrograph

We review the advantages of using hot white dwarfs (WDs) as probes of the deuterium abundance in the local interstellar medium. We then discuss advantages of the Space Telescope Imaging Spectrograph (STIS) for such observations, as compared with earlier observations with the Goddard High Resolution Spectrograph (GHRS). The GHRS Ly α profile of the white dwarf HZ 43 is probably modified by the hot ‘hydrogen wall’ surrounding the Sun; but despite this complication, the sightline remains a promising one for an accurate determination of the deuterium abundance in the local interstellar medium.

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