Galactic Interstellar Gas Cloud Mass Functions: A Simple Quantitative Approach

2007 ◽  
Vol 656 (2) ◽  
pp. 897-906 ◽  
Author(s):  
E. Casuso ◽  
J. E. Beckman
Keyword(s):  
Quantitative Approach ◽  
Interstellar Gas ◽  
Gas Cloud ◽  
Mass Functions

The Main Sequence Evolution of Inhomogeneous Stars

1982 ◽  
Vol 4 (4) ◽  
pp. 396-400 ◽  
Author(s):  
J. Lattanzio
Keyword(s):  
Gravitational Collapse ◽  
Heavy Element ◽  
Main Sequence ◽  
Element Abundance ◽  
Sequence Evolution ◽  
Interstellar Gas ◽  
Convective Mixing ◽  
The Core ◽  
Gas Cloud

Duley (1974) has shown that, at the temperatures usually associated with interstellar gas clouds, we would expect CNO grains to be present. During gravitational collapse these grains migrate to the centre of the gas cloud, leading to an enhancement of the heavy-element abundance in the core (Prentice 1976, 1978). It was Krautschneider (1977) who verified such a scenario, by considering the dynamical collapse of gas and grain clouds. If such an initial radial abundance inhomogeneity existed, Prentice (1976a) showed that this configuration may well survive the later convective mixing phase and thus approach the zero-age main-sequence (ZAMS) with a small (-v 3% by mass) metal enhanced core.

scholarly journals The collapse of a fast rotating interstellar gas cloud

1983 ◽  
Vol 203 (2) ◽  
pp. 491-515 ◽  
Author(s):  
S. Narita ◽  
D. McNally ◽  
G. L. Pearce ◽  
S. A. Sorensen
Keyword(s):  
Interstellar Gas ◽  
Gas Cloud ◽  
Fast Rotating

scholarly journals Magnetic Effects in Clouds

1992 ◽  
Vol 45 (4) ◽  
pp. 531 ◽  
Author(s):  
L Mestel
Keyword(s):  
Flux Ratio ◽  
High Mass ◽  
Interstellar Gas ◽  
Magnetic Forces ◽  
T Tauri ◽  
Low Degree ◽  
Magnetic Buoyancy ◽  
Gas Cloud ◽  
Flux Leakage ◽  
Maxwell Stresses

A realistic study of the structure and evolution of an interstellar gas cloud must take cognisance of the flux from the galactic magnetic field threading the cloud. If the non-dimensional mass-to-flux ratio is below a critical value, the forces exerted by the locally distorted field can balance gravity in the two trans-field dimensions, while Alfvenic turbulent motions yield support along the field. A super-critical cloud, collapsing with its flux virtually frozen in, may fragment into sub-condensations following spontaneous flattening along the field. Within a sub-critical molecular cloud, the very low degree of ionisation allows the magnetic forces to redistribute flux through the cloud, so that locally denser regions may become super-critical and condense out of the cloud. The Maxwell stresses also transport angular momentum efficiently from a slowly contracting condensation to the surroundings. If flux leakage remains slow throughout all the pre-opaque phases, the magnetic forces and the associated turbulent motions may shift the ultimate mass spectrum towards the high mass end. Most of the remnant flux may be lost by magnetic buoyancy during the pre-main sequence epoch, so possibly supplying a power source for the T Tauri phenomenon.

scholarly journals Isotopic imprint of the Solar system encounter with interstellar gas cloud around 660 BC (2610 BP)

2019 ◽  
Vol 1400 ◽  
pp. 022034
Author(s):  
A K Pavlov ◽  
A V Blinov ◽  
D A Frolov ◽  
A N Konstantinov ◽  
I V Koudriavtsev ◽  
...  
Keyword(s):  
Solar System ◽  
Interstellar Gas ◽  
Gas Cloud

scholarly journals On the Theory of Rotating Magnetic Stars

1970 ◽  
Vol 4 ◽  
pp. 264-268
Author(s):  
G. A. E. Wright
Keyword(s):  
Magnetic Field ◽  
Low Energy ◽  
Early Type ◽  
Interstellar Gas ◽  
Yield Information ◽  
Magnetic Stars ◽  
Strong Surface ◽  
Early Type Stars ◽  
Surface Convection ◽  
Gas Cloud

AbstractAll observations of magnetic stars necessarily yield information only about their surface features. We are ignorant of the nature of the fields in the interiors of such stars, and equally we cannot be sure of the non-existence of interior fields in stars which are superficially non-magnetic. In fact, if we assume the truth of the ‘fossil’ theory – that the magnetic flux of an Ap star is a relic of the flux initially present in the gas cloud from which the star condensed – then it is surprising that magnetic stars are not observed to be much more common, since magnetic fields appear to be ubiquitous in interstellar gas clouds. For those stars with strong surface convection zones, we might expect that a fossil field of low energy would be expelled by the turbulence and would possibly be trapped in the interior. However, the majority of early-type stars with radiative envelopes also do not exhibit any observable magnetic field.

Nucleosynthesis and the origin of the elements

1988 ◽  
Vol 325 (1587) ◽  
pp. 391-403 ◽  
Keyword(s):  
Solar System ◽  
Solar Nebula ◽  
Raw Material ◽  
Fine Scale ◽  
Fusion Reactions ◽  
Interstellar Gas ◽  
Incomplete Mixing ◽  
Nuclear Fusion Reactions ◽  
Gas Cloud ◽  
Isotopic Anomalies

Stars obtain their energy from nuclear-fusion reactions and these reactions can produce most elements and isotopes up to the neighbourhood of iron in the periodic table. Most more massive elements are also believed to be produced in stars by reactions involving the addition of neutrons. Mass loss from stars, both castastrophic and gradual, returns processed matter to the interstellar medium and in this way the raw material for the Solar System was assembled. It was originally believed that the Solar System was formed from a gas cloud that was chemically and isotopically homogeneous, with the variation of composition of objects today being attributed to processes occurring in the solar nebula. This was changed by the discovery of isotopic anomalies in meteorites. It is now clear that there was some departure from fine-scale mixing in the solar nebula. This may have resulted from late irradiation by a supernova or from the survival of interstellar grains with particular nucleosynthetic origins, or both, as well as from incomplete mixing of the interstellar gas.

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