scholarly journals Composition of matter in the heliosphere

2008 ◽  
Vol 4 (S257) ◽  
pp. 17-28 ◽  
Author(s):  
Peter Bochsler
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Galactic Center ◽  
Compositional Data ◽  
The Other ◽  
The Sun ◽  
Pickup Ions ◽  
Solar Composition ◽  
The Galaxy ◽  
State Composition

AbstractThe Sun is by far the largest reservoir of matter in the solar system and contains more than 99% of the mass of the solar system. Theories on the formation of the solar system maintain that the gravitational collapse is very efficient and that typically not more than one tenth from the solar nebula is lost during the formation process. Consequently, the Sun can be considered as a representative sample of interstellar matter taken from a well mixed reservoir 4.6 Gy ago, at about 8 kpc from the galactic center. At the same time, the Sun is also a faithful witness of the composition of matter at the beginning of the evolution of the solar system and the formation of planets, asteroids, and comets. Knowledge on the solar composition and a fair account of the related uncertainties is relevant for many fields in astrophysics, planetary sciences, cosmo- and geochemistry. Apart from the basic interest in the chemical evolution of the galaxy and the solar system, compositional studies have also led to many applications in space research, i.e., it has helped to distinguish between different components of diffuse heliospheric matter. The elemental, isotopic, and charge state composition of heliospheric particles (solar wind, interstellar neutrals, pickup ions) has been used for a multitude of applications, such as tracing the source material, constraining parameters for models of the acceleration processes, and of the transport through the interplanetary medium. It is important to realize, that the two mainstream applications, as outlined above – geochemistry and cosmochemistry on one side, and tracing of heliospheric processes on the other side – are not independent of each other. Understanding the physical processes, e.g., of the fractionation of the solar wind, is crucial for the interpretation of compositional data; on the other hand, reliable information on the source composition is the basis for putting constraints on models of the solar wind fractionation.

On the Color Excesses of Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 529-530
Author(s):  
V. Straižys ◽  
R. Janulis
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Galactic Center ◽  
Galactic Plane ◽  
The Other ◽  
The Sun ◽  
General Direction ◽  
Dust Layer ◽  
Color Indices ◽  
The Galaxy

The interstellar reddening of globular clusters of the Galaxy is still an important unresolved problem, especially for metal-rich objects that are found usually at low galactic latitudes in the general direction of the galactic center. Their color excesses are needed in order to correct their color-magnitude diagrams and to determine their intrinsic integrated color indices. For this we need some method which is not related to measures of the cluster stars. One such method is to use foreground field stars in the direction of the globular cluster to measure the interstellar reddening. Because most of the globular clusters lie outside the galactic plane, we need information about the reddening in all the layer of absorbing dust in different directions. This information can be obtained by investigating stars which are at different distances from the Sun up to the edge of the absorbing dust layer. On the other hand, these stars should be as close as possible to the position of the globular cluster to avoid possible variations in the interstellar reddening in the area of the cluster.

scholarly journals Pulsars as a galactic population

1979 ◽  
Vol 84 ◽  
pp. 119-123
Author(s):  
Joseph H. Taylor
Keyword(s):  
Carbon Monoxide ◽  
Statistical Analysis ◽  
Supernova Remnants ◽  
Galactic Center ◽  
Hii Regions ◽  
The Sun ◽  
Disk Thickness ◽  
Galactic Population ◽  
The Galaxy

Recent pulsar surveys have increased the number of known pulsars to well over 300, and many of them lie at distances of several kpc or more from the sun. The distribution of pulsars with respect to distance from the galactic center is similar to other population I material such as HII regions, supernova remnants, and carbon monoxide gas, but the disk thickness of the pulsar distribution is rather greater, with <|z|>≈350 pc. Statistical analysis suggests that the total number of active pulsars in the Galaxy is a half million or more, and because kinematic arguments require the active lifetimes of pulsars to be ≲5×106 years, it follows that the birthrate required to maintain the observed population is one pulsar every ∼10 years (or less) in the Galaxy.

scholarly journals 11. The Role of Protoplanets in the Formation of the Solar System

1977 ◽  
Vol 39 ◽  
pp. 569-571
Author(s):  
I. P. Williams
Keyword(s):  
Solar System ◽  
Refractory Material ◽  
The Sun ◽  
Resisting Medium ◽  
Solar Composition ◽  
Roche Limit ◽  
Natural Outcome

A likely origin of the asteroids (and possibly, of the comets?) is the natural outcome of the following scenario that we propose for the formation of the planets. Protoplanets of similar mass and solar composition will segregate in three different ways: For those far enough from the sun (like Uranus and Neptune), the segregation of icy grains releases enough energy to drive the remaining gases to infinity. For all other planets, the segregation of refractory material only does not release enough energy to disrupt the protoplanet; however, while spiraling inwards in a resisting medium, the terrestrial protoplanets cross their Roche limit and lose their gaseous outer layers. Asteroids (or comets) could therefore originate from the disruption of protoplanets before the settling of their refractory (or icy) grains is completed.

scholarly journals Classical Absolute/Differential Programs

1986 ◽  
Vol 7 ◽  
pp. 77-80
Author(s):  
L V Morrison
Keyword(s):  
Solar System ◽  
Ab Initio ◽  
Reference Frames ◽  
Mechanical Systems ◽  
The Other ◽  
Frames Of Reference ◽  
Rotating Frame ◽  
Absolute Differential ◽  
The Galaxy

In astronomy we try to determine a non-rotating frame from analyses of the observed motions of three mechanical systems – the solar system, the galaxy and the extragalactic nebulae. The rotation of the extragalactic frame is of the order 10-10 arcsec per century, so, for all practical purposes, this frame may be regarded as having no rotation. The other two frames are model-dependent and, as such, cannot be regarded ab initio as constituting non-rotation frames of reference. These reference frames are linked by various techniques, as shown in the diagram below.

scholarly journals A New Value for the Rotation Speed of the Spiral Structure

1977 ◽  
Vol 45 ◽  
pp. 293-296 ◽  
Author(s):  
J. Palouš
Keyword(s):  
Surface Density ◽  
Galactic Center ◽  
Local Density ◽  
Outer Part ◽  
Density Variation ◽  
The Sun ◽  
Basic Model ◽  
Rr Lyrae ◽  
The Galaxy ◽  
Nearby Stars

The basic model of our Galaxy, like the Schmidt (1965) model, obeys the density law ρ(R) for the Galaxy based on divers evidence, less or better known from observation. The interpretation of the interstellar hydrogen radio profiles yields the rotation curve and the run of the force component in the radial direction. The Oort constants A, B known from radial velocities and proper motions of nearby stars, the distance from the Sun to the galactic center Roestablished from the distances of RR Lyrae stars, the local density and density gradients in the vicinity of the Sun, known from the star counts, are involved in this basic model of the Galaxy. The r.m.s. velocity component in the z direction yields the approximate mass distribution in this direction. The model surface density is computed by integrating the density along the z direction in the model. The local surface density in the Schmidt model is 114 solar masses per pc2; it depends rather strongly on the assumed density variation in the outer part of the Galaxy.

scholarly journals XII. Radiation in the solar system: its effect on temperature and its pressure on small bodies

1904 ◽  
Vol 202 (346-358) ◽  
pp. 525-552 ◽  
Keyword(s):  
Solar System ◽  
Power Law ◽  
Effective Temperature ◽  
Interplanetary Space ◽  
The Other ◽  
Fourth Power ◽  
The Sun ◽  
Planetary Surfaces ◽  
Solar Constant ◽  
Small Bodies

When a surface is a full radiator and absorber its temperature can be determined at once by the fourth-power law if we know the rate at which it is radiating energy. If it is radiating what it receives from the sun, then a knowledge of the solar constant enables us to find the temperature. We can thus make estimates of the highest temperature which a surface can reach when it is only receiving heat from the sun. We can also make more or less approximate estimates of the temperatures of the planetary surfaces by assuming conditions under which the radiation takes place, and we can determine, fairly exactly, the temperatures of very small bodies in interplanetary space. These determinations require a knowledge of the constant of radiation and of either the solar constant or the effective temperature of the sun, either of which, as is well known, can be found from the other by means of the radiation constant. It will be convenient to give here the values of these quantities before proceeding to apply them to our special problems.

scholarly journals Abundances of hydrogen and helium isotopes in the Protosolar Cloud

2009 ◽  
Vol 5 (S268) ◽  
pp. 71-79 ◽  
Author(s):  
Johannes Geiss ◽  
George Gloeckler
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Big Bang ◽  
The Sun ◽  
Density Profiles ◽  
Origin And Evolution ◽  
Naturally Occurring ◽  
System 2 ◽  
The Big Bang ◽  
The Universe

AbstractFor our understanding of the origin and evolution of baryonic matter in the Universe, the Protosolar Cloud (PSC) is of unique importance in two ways: 1) Up to now, many of the naturally occurring nuclides have only been detected in the solar system. 2) Since the time of solar system formation, the Sun and planets have been virtually isolated from the galactic nuclear evolution, and thus the PSC is a galactic sample with a degree of evolution intermediate between the Big Bang and the present.The abundances of the isotopes of hydrogen and helium in the Protosolar Cloud are primarily derived from composition measurements in the solar wind, the Jovian atmosphere and “planetary noble gases” in meteorites, and also from observations of density profiles inside the Sun. After applying the changes in isotopic and elemental composition resulting from processes in the solar wind, the Sun and Jupiter, PSC abundances of the four lightest stable nuclides are given.

scholarly journals The Cosmological Decrease of Galactic Density and the Induced Retarded Gravity Effect on Rotation Curves

2021 ◽  
Author(s):  
Asher Yahalom
Keyword(s):  
Dark Matter ◽  
Galactic Center ◽  
Temporal Change ◽  
The Other ◽  
Local Effects ◽  
Physical Systems ◽  
Cosmic Expansion ◽  
The Galaxy ◽  
Action At A Distance ◽  
Retardation Effects

Galaxies are huge physical systems having dimensions of many tens of thousands of light years. Thus any change at the galactic center will be noticed at the rim only tens of thousands of years later. Those retardation effects seems to be neglected in present day galactic modelling used to calculate rotational velocities of matter in the rims of the galaxy and surrounding gas. The significant differences between the predictions of Newtonian instantaneous action at a distance and observed velocities are usually explained by either assuming dark matter or by modifying the laws of gravity (MOND). In this paper we will show that taking general relativity seriously without neglecting retardation effects one can explain the radial velocities of galactic matter without postulating dark matter. However, this will rely on a temporal change of galactic mass. We will compare two different mechanisms of density change, one is local, that is accretion of matter from the intergalactic medium. The other is global, that is the cosmological decrease of density due to the cosmic expansion. It will be shown that local effects are much more important in this respect.

The Rotation Curve from A-F Supergiants

1996 ◽  
Vol 169 ◽  
pp. 703-706
Author(s):  
D. M. Peterson ◽  
D. Slowik
Keyword(s):  
Total Mass ◽  
Rotation Curve ◽  
Galactic Center ◽  
Galactic Rotation ◽  
The Sun ◽  
Critical Information ◽  
New Class ◽  
The Galaxy ◽  
Local Distance

The Galactic rotation law provides critical information for estimating the distribution of mass in the Galaxy, for tying the distance of the Sun from the Galactic center to local distance scales, and, if determined over large enough distances, for estimating the total mass of the system and the amount of nonluminous matter present. Interior to the Sun velocities are well defined by observations of the ISM, particularly HI. These techniques are not available for points exterior to the Sun and we must rely on observations of velocities of objects whose distances can be estimated. Notable among these are the Cepheids (Pont et al 1994) and the combination of CO velocities and OB cluster distances (Brand & Blitz 1993) where the two are found to coexist. Adding a new class of objects, particularly bright, relatively common objects to this effort is of importance.

Interaction of the Planets through the Solar Wind

1967 ◽  
Vol 1 (1) ◽  
pp. 5-6 ◽  
Author(s):  
E. G. Bowen
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
The Sun ◽  
Gravitational Forces

It is usual to describe the motion of the planets around the sun in terms only of the gravitational forces between them. The purpose of this note is to point out that another form of interaction between bodies in the solar system is possible through the medium of the solar wind.

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