scholarly journals Mathematical model for the 0.5 billion years aged Sun

2000 ◽  
pp. 35-40
Author(s):  
E. Tatomir
Keyword(s):  
Energy Source ◽  
Mathematical Model ◽  
Numerical Integration ◽  
Main Sequence ◽  
Solar Model ◽  
System Of Equations ◽  
The Sun ◽  
Solar Mass ◽  
Proton Proton ◽  
Close Vicinity

An algorithm is given for constructing evolutionary tracks for a star with the mass equal to one solar mass. The presented model can be applied to the stars belonging to the inferior main sequence, which have the proton-proton reaction as energy source and present a radiative core and a convective shell. This paper presents an original way of solving the system of equations corresponding to the radiative nucleus by using Taylor?s series in close vicinity to the center of the Sun. It also presents the numerical integration and the results for a 0.5 billion years aged solar model.

scholarly journals Mass-loss varying luminosity and its implication to the solar evolution

2019 ◽  
Vol 15 (S356) ◽  
pp. 403-404
Author(s):  
Negessa Tilahun Shukure ◽  
Solomon Belay Tessema ◽  
Endalkachew Mengistu
Keyword(s):  
Standard Model ◽  
Mass Loss ◽  
Main Sequence ◽  
The Sun ◽  
Solar Mass ◽  
Solar Luminosity ◽  
Solar Evolution

AbstractSeveral models of the solar luminosity, , in the evolutionary timescale, have been computed as a function of time. However, the solar mass-loss, , is one of the drivers of variation in this timescale. The purpose of this study is to model mass-loss varying solar luminosity, , and to predict the luminosity variation before it leaves the main sequence. We numerically computed the up to 4.9 Gyrs from now. We used the solution to compute the modeled . We then validated our model with the current solar standard model (SSM). The shows consistency up to 8 Gyrs. At about 8.85 Gyrs, the Sun loses 28% of its mass and its luminosity increased to 2.2. The model suggests that the total main sequence lifetime is nearly 9 Gyrs. The model explains well the stage at which the Sun exhausts its central supply of hydrogen and when it will be ready to leave the main sequence. It may also explain the fate of the Sun by making some improvements in comparison to previous models.

scholarly journals Some Aspects of Constructing Long Ephemerides of the Sun, Major Planets and the Moon: Ephemeris AE95

1997 ◽  
Vol 165 ◽  
pp. 245-250
Author(s):  
G.I. Eroshkin ◽  
N.I. Glebova ◽  
M.A. Fursenko ◽  
A. A. Trubitsina
Keyword(s):  
Mathematical Model ◽  
Solar System ◽  
Numerical Integration ◽  
High Precision ◽  
The Sun ◽  
Specific Character ◽  
The Moon ◽  
Special Edition ◽  
Polynomial Representation

The construction of long-term numerical ephemerides of the Sun, major planets and the Moon is based essentially on the high-precision numerical solution of the problem of the motion of these bodies and polynomial representation of the data. The basis of each ephemeris is a mathematical model describing all the main features of the motions of the Sun, major planets, and Moon. Such mathematical model was first formulated for the ephemerides DE/LE and was widely applied with some variations for several national ephemeris construction. The model of the AE95 ephemeris is based on the DE200/LE200 ephemeris mathematical model. Being an ephemeris of a specific character, the AE95 ephemeris is a basis for a special edition “Supplement to the Astronomical Yearbook for 1996–2000”, issued by the Institute of the Theoretical Astronomy (ITA) (Glebova et al., 1995). This ephemeris covering the years 1960–2010 is not a long ephemeris in itself but the main principles of its construction allow one to elaborate the long-term ephemeris on an IBM PC-compatible computer. A high-precision long-term numerical integration of the motion of major bodies of the Solar System demands a choice of convenient variables and a high-precision method of the numerical integration, taking into consideration the specific features of both the problem to be solved and the computer to be utilized.

Elemental high-precision abundances as function of stellar ages: Constrains on the Galactic chemical evolution

2017 ◽  
Vol 13 (S334) ◽  
pp. 376-377
Author(s):  
Marcelo Tucci Maia
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Chemical Elements ◽  
The Sun ◽  
Galactic Chemical Evolution ◽  
Special Group ◽  
Solar Mass ◽  
Differential Abundance ◽  
Stellar Ages ◽  
The Galaxy

AbstractSolar twins are a special group of stars that have spectra and stellar parameters very close to the Sun. Also having mass around 1 solar mass and roughly solar chemical composition, these stars follow a similar evolutionary path to the Sun, from the zero age main sequence to the end of their lives. Additional to that, the similarity between themselves permit us to obtain high-precision differential abundance and thus, very precise atmospheric parameters that allows a reliable estimation of their ages using the traditional isochronal method. Taking advantage of this very restrict group of stars we can better understand the effects of nucleosynthesis of chemical elements throughout the Galaxy and with this, finding constrains for its evolution.

EARLY AND MAIN SEQUENCE EVOLUTION OF STARS IN THE RANGE 0.5 TO 100 SOLAR MASSES

1967 ◽  
Vol 45 (11) ◽  
pp. 3429-3460 ◽  
Author(s):  
Dilhan Ezer ◽  
A. G. W. Cameron
Keyword(s):  
Mass Loss ◽  
Main Sequence ◽  
Mass Range ◽  
Energy Stability ◽  
Sequence Evolution ◽  
The Sun ◽  
Solar Mass ◽  
Mass Model ◽  
Evolutionary Study ◽  
Evolutionary Studies

The evolutionary study previously carried out for the sun has been extended to stars of 0.5, 0.7, 2, 5, 10, 20, 50, and 100 solar masses. The evolutionary calculations were started at the threshold of energy stability, carried through the approach to the main sequence, and (with the exception of the 100 solar-mass model) through the depletion of hydrogen on the main sequence. All models were observed to have a completely convective Hayashi phase. There was general agreement, in the appropriate mass range, with the evolutionary studies of Iben, the discrepancies apparently resulting from different opacities used in the calculations. Lines of equal evolutionary age in a Hertzsprung–Russell diagram constructed from these calculations do not agree with the observations of Walker, probably because of the neglect of mass loss and rotation in the early stellar evolutionary histories.

scholarly journals On the mass distribution of stars in the solar neighborhood

2006 ◽  
pp. 17-20 ◽  
Author(s):  
S. Ninkovic ◽  
V. Trajkovska
Keyword(s):  
Mass Distribution ◽  
Main Sequence ◽  
Solar Neighborhood ◽  
The Sun ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Low Mass ◽  
The Mean

The present authors analyze samples consisting of Hipparcos stars. Based on the corresponding HR diagrams they estimate masses of Main-Sequence stars from their visual magnitudes. They find that already beyond the heliocentric radius of 10 pc the effects of observational selection against K and M dwarfs become rather strong. For this reason the authors are inclined to think that the results concerning this heliocentric sphere appear as realistic, i. e. the fraction of low-mass stars (under half solar mass) is about 50% and, as a consequence, the mean star mass should be about 0.6 solar masses and Agekyan's factor about 1.2. That stars with masses higher than 5 M? are very rare is confirmed also from the data concerning more remote stars. It seems that white dwarfs near the Sun are not too frequent so that their presence cannot affect the main results of the present work significantly.

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

Electrolysis of Wastewater - A Laboratory Study

1975 ◽  
Vol 10 (1) ◽  
pp. 214-223
Author(s):  
N.S. Wei ◽  
G.W. Heinke
Keyword(s):  
Energy Source ◽  
Mathematical Model ◽  
Stainless Steel ◽  
Charge Density ◽  
Energy Requirement ◽  
Phosphate Removal ◽  
Septic Tank ◽  
Metallic Ions ◽  
Treatment Unit ◽  
Consumable Electrodes

Abstract This paper presents bench scale experimental results on the electrolysis of raw domestic wastewater. Studies carried out with consumable electrodes are discussed. A mathematical model of a small electrolytic sewage treatment unit for individual household application is developed. The energy consumption and cost of such a device are discussed. Electrolysis can be described as a process in which chemical reactions are induced at each electro-liquid interface by applying an external electrical energy source to a system of electrodes immersed in a liquid. This paper deals only with electrolysis where a direct current power supply is used as the energy source. The process is governed by Faraday' s two laws on electrochemistry. The fundamental process parameter is the electrical charge density, measured as coulombs per litre (c/1) of wastewater treated. There are two basic types of electrolysis depending on the choice of anode material. When the anode is made of dissolvable metallic material such as iron, stainless steel and aluminum, the metal dissolves and goes into the sewage as metallic ions and forms hydrated metallic oxides which act as flocculating agents. The amount of metal dissolved is proportional to the quantity of electrical charges supplied to the system. Results from a series of batch experiments showed that electrolysis with consumable electrodes is capable of removing significant amounts of organic pollutants. Total organic carbon (TOC) removal was found to be a function of charge density. Phosphate removal efficiency of 90 percent or higher was achieved at a relatively low charge density of 240 coulombs per litre with either iron or stainless steel anodes. A mathematical model was derived in the conceptual design of a household electrolytic treatment unit. The model incorporates variables such as decomposition voltage of the electrodes and electrical conductivity of the wastewater as well as the physical configuration of the electrolytic cell. The energy requirement of such a unit can be calculated from the model. It is suggested in this paper that an electrolytic waste treatment unit could be an alternative to the septic tank and tile bed system in areas where the latter is not applicable due to poor soil and terrain conditions.

Much Ado about (Practically) Nothing

2010 ◽  
Author(s):  
David Fisher
Keyword(s):  
Energy Source ◽  
Atomic Nucleus ◽  
The Sun ◽  
Scientific Journals ◽  
Rare Gases ◽  
Important Work ◽  
The Earth ◽  
Wide Range ◽  
Life On Mars ◽  
The Universe

There are eight columns in the Periodic Table. The eighth column is comprised of the rare gases, so-called because they are the rarest elements on earth. They are also called the inert or noble gases because, like nobility, they do no work. They are colorless, odorless, invisible gases which do not react with anything, and were thought to be unimportant until the early 1960s. Starting in that era, David Fisher has spent roughly fifty years doing research on these gases, publishing nearly a hundred papers in the scientific journals, applying them to problems in geophysics and cosmochemistry, and learning how other scientists have utilized them to change our ideas about the universe, the sun, and our own planet. Much Ado about (Practically) Nothing will cover this spectrum of ideas, interspersed with the author's own work which will serve to introduce each gas and the important work others have done with them. The rare gases have participated in a wide range of scientific advances-even revolutions-but no book has ever recorded the entire story. Fisher will range from the intricacies of the atomic nucleus and the tiniest of elementary particles, the neutrino, to the energy source of the stars; from the age of the earth to its future energies; from life on Mars to cancer here on earth. A whole panoply that has never before been told as an entity.

Fusion in the Sun

2018 ◽  
Author(s):  
E. L. Wolf
Keyword(s):  
Kinetic Energy ◽  
Power Density ◽  
Dense Plasma ◽  
Alpha Particles ◽  
The Sun ◽  
Proton Proton ◽  
Atomic Nuclei ◽  
Proton Fusion ◽  
Schrödinger's Equation ◽  
Simplified Formula

Protons in the Sun’s core are a dense plasma allowing fusion events where two protons initially join to produce a deuteron. Eventually this leads to alpha particles, the mass-four nucleus of helium, releasing kinetic energy. Schrodinger’s equation allows particles to penetrate classically forbidden Coulomb barriers with small but important probabilities. The approximation known as Wentzel–Kramers–Brillouin (WKB) is used by Gamow to predict the rate of proton–proton fusion in the Sun, shown to be in agreement with measurements. A simplified formula is given for the power density due to fusion in the plasma constituting the Sun’s core. The properties of atomic nuclei are briefly summarized.

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