scholarly journals Variations in Solar Radiation and the Cause of Ice Ages

1950 ◽  
Vol 1 (08) ◽  
pp. 453-455 ◽  
Author(s):  
F. Hoyle ◽  
R. A. Lyttleton
Keyword(s):  
Solar Radiation ◽  
Stellar Evolution ◽  
Recent Progress ◽  
Solar Surface ◽  
The Sun ◽  
Total Radiation ◽  
Ice Ages ◽  
Gravitational Action ◽  
Extra Energy ◽  
Possible Cause

Abstract Most astronomical hypotheses on the causes of ice ages are dynamically untenable. Alterations in the amount of solar radiation, however, have long been recognized as a possible cause, but only with recent progress in the theory of stellar evolution has it become clear that such changes must occur. At irregular intervals the sun will pass, and will have passed, with low relative speeds through interstellar hydrogen clouds, and the gravitational action of the sun leads to an increase in the quantity of material falling to the surface with high velocity. The conversion of the kinetic energy of fall of this material results in an increase of emission at the solar surface. Increases of order up to about 10 per cent of the present total radiation could occur, and the process is such that the extra energy would be located mainly in the shorter wavelengths.

scholarly journals Variations in Solar Radiation and the Cause of Ice Ages

1950 ◽  
Vol 1 (8) ◽  
pp. 453-455
Author(s):  
F. Hoyle ◽  
R. A. Lyttleton
Keyword(s):  
Solar Radiation ◽  
Stellar Evolution ◽  
Recent Progress ◽  
Solar Surface ◽  
The Sun ◽  
Total Radiation ◽  
Ice Ages ◽  
Gravitational Action ◽  
Extra Energy ◽  
Possible Cause

AbstractMost astronomical hypotheses on the causes of ice ages are dynamically untenable. Alterations in the amount of solar radiation, however, have long been recognized as a possible cause, but only with recent progress in the theory of stellar evolution has it become clear that such changes must occur. At irregular intervals the sun will pass, and will have passed, with low relative speeds through interstellar hydrogen clouds, and the gravitational action of the sun leads to an increase in the quantity of material falling to the surface with high velocity. The conversion of the kinetic energy of fall of this material results in an increase of emission at the solar surface. Increases of order up to about 10 per cent of the present total radiation could occur, and the process is such that the extra energy would be located mainly in the shorter wavelengths.

scholarly journals The Rotation of the Solar Radiative zone

2008 ◽  
Vol 4 (S252) ◽  
pp. 257-258
Author(s):  
S. Turck-Chieze
Keyword(s):  
Stellar Evolution ◽  
Recent Progress ◽  
Solar Rotation ◽  
Present Knowledge ◽  
The Sun ◽  
Dynamical Processes ◽  
Radiative Zone

AbstractDynamical processes are progressively introduced in stellar evolution. In this framework, the Sun is a very specific case where both models and observations have been developed in parallel during the last decade in order to progress on our present insight of solar like stars. In this poster I show the recent progress done on both sides for the rotation of the radiative zone. The present knowledge of the solar rotation profile comes from the detection of acoustic and gravity modes with the instruments GOLF and MDI aboard SoHO. In parallel we study the sensitivity of the theoretical rotation profiles obtained with the CESAM code using different rotation history in the premainsequence.

Gaia or Athena? The Early Faint-Sun Paradox

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Carbon Dioxide ◽  
Solar Radiation ◽  
Surface Temperature ◽  
Stellar Evolution ◽  
The Sun ◽  
Solar Luminosity ◽  
The Past ◽  
The Earth ◽  
Climate Evolution

Stellar evolution theory predicts large, long-term solar large, long-term solar luminosity (L⊙) changes over the lifetime of the sun. The most certain prediction is a general monotonic increase (neglecting short-period variations) in L⊙ of about 30% over the past 4.7 billion years, an increase that will continue. This prediction is well founded theoretically (based on the conversion of hydrogen into heavier elements) and supported observationally by the famous Hertzsprung-Russell diagram showing stellar evolution. If the solar luminosity increases monotonically with time, one might expect to find evidence of increasing surface temperatures in the Earth’s paleoclimatic record. Instead, isotopic indicators show Earth’s mean surface temperature is now significantly lower than it was 3 billion years ago. In 1975, R. K. Ulrich termed this the “faint young sun” paradox. Simultaneous solar luminosity increase and terrestrial temperature decrease imply additional strong influences on climate evolution. To understand climate evolution (and, by inference, the present climate), we must first determine the nature of these “compensatory mechanisms.” The positively increasing line in Figure 12.1 shows the evolution of solar luminosity (in units of present luminosity, L). Since terrestrial surface temperatures have remained nearly constant during the last 2.3 billion years, this requires a very effective compensatory mechanism. Several theories attempt to explain why the Earth’s surface temperature has remained relatively constant even while the solar luminosity has increased by 30%. Also, various scenarios have been advanced to explain why the Earth remained ice-free even during periods when the sun was much dimmer than it is today. Some of these ideas are: • Since it had fewer continents and more oceans, the early Earth was much darker. This same darker surface absorbed enough additional incoming solar radiation to remain ice-free. • In the past, energy transport from the equator to polar regions was easier because the continents had lower elevations. This enhanced heat transport allowed the Earth to remain relatively warm. • The early atmosphere had more carbon dioxide and methane, creating an enhanced greenhouse effect sufficient to trap the incoming solar radiation and keep the Earth warm. The enormous amount of carbon trapped in limestone suggests that Earth’s former atmosphere contained much more carbon dioxide than it does today.

The effect of interstellar matter on climatic variation

1939 ◽  
Vol 35 (3) ◽  
pp. 405-415 ◽  
Author(s):  
F. Hoyle ◽  
R. A. Lyttleton
Keyword(s):  
Solar Radiation ◽  
Relative Velocity ◽  
Solar Surface ◽  
Climatic Variation ◽  
Ice Age ◽  
Interstellar Matter ◽  
The Sun ◽  
High Increase ◽  
Appreciable Change

The effect of interstellar matter on the sun's radiation is considered with a view to explaining changes in terrestrial climate. It appears that a star in passing through a nebulous cloud will capture an amount of material which by the energy of its fall to the solar surface can bring about considerable changes in the quantity of radiation emitted. The quantity of matter gathered in by the star depends directly on the density of the cloud and inversely on the cube of its velocity relative to the cloud. Thus vastly different effects on the solar radiation can be brought about under fairly narrow ranges of density and relative velocity (ranges that are in accordance with astronomical evidence). In this way the process is able to explain the small changes in the solar radiation that are necessary to produce an ice age and, under conditions less likely to have taken place frequently, the high increase in radiation required for the Carboniferous Epoch. Despite the large effects that the mechanism can bring about, it is shown that the mass of the sun does not undergo appreciable change and hence reverts to its former luminosity once the cloud has been traversed.

The9Be Abundances of α Centauri A and B and the Sun: Implications for Stellar Evolution and Mixing

1997 ◽  
Vol 478 (2) ◽  
pp. 778-786 ◽  
Author(s):  
Jeremy R. King ◽  
Constantine P. Deliyannis ◽  
Ann Merchant Boesgaard
Keyword(s):  
Stellar Evolution ◽  
The Sun

scholarly journals Solar structure and evolution

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Jørgen Christensen-Dalsgaard
Keyword(s):  
Solar Surface ◽  
Solar Neutrinos ◽  
Solar Interior ◽  
Stellar Structure ◽  
The Sun ◽  
Physical Processes ◽  
Solar Evolution ◽  
Internal Properties ◽  
Atmospheric Phenomena

AbstractThe Sun provides a critical benchmark for the general study of stellar structure and evolution. Also, knowledge about the internal properties of the Sun is important for the understanding of solar atmospheric phenomena, including the solar magnetic cycle. Here I provide a brief overview of the theory of stellar structure and evolution, including the physical processes and parameters that are involved. This is followed by a discussion of solar evolution, extending from the birth to the latest stages. As a background for the interpretation of observations related to the solar interior I provide a rather extensive analysis of the sensitivity of solar models to the assumptions underlying their calculation. I then discuss the detailed information about the solar interior that has become available through helioseismic investigations and the detection of solar neutrinos, with further constraints provided by the observed abundances of the lightest elements. Revisions in the determination of the solar surface abundances have led to increased discrepancies, discussed in some detail, between the observational inferences and solar models. I finally briefly address the relation of the Sun to other similar stars and the prospects for asteroseismic investigations of stellar structure and evolution.

scholarly journals Inclusion of a time-dependent, non-local convection theory in a stellar evolution code

2006 ◽  
Vol 2 (S239) ◽  
pp. 314-316 ◽  
Author(s):  
Achim Weiss ◽  
Martin Flaskamp
Keyword(s):  
Velocity Field ◽  
Local Time ◽  
Stellar Evolution ◽  
Time Dependent ◽  
Test Cases ◽  
The Sun ◽  
Specific Test ◽  
Non Local ◽  
Convective Boundaries

AbstractThe non-local, time-dependent convection theory of Kuhfuß (1986) in both its one- and three-equation form has been implemented in the Garching stellar evolution code. We present details of the implementation and the difficulties encountered. Specific test cases have been calculated, among them a 5 M⊙ star and the Sun. These cases point out deficits of the theory. In particular, the assumption of an isotropic velocity field leads to too extensive overshooting and has to be modified at convective boundaries. Some encouraging aspects are indicated as well.

Evolution of Comets into Asteroids?

1971 ◽  
Vol 12 ◽  
pp. 413-421 ◽  
Author(s):  
B.G. Marsden
Keyword(s):  
Solar Radiation ◽  
Solar Nebula ◽  
Oort Cloud ◽  
Original Version ◽  
Terrestrial Planets ◽  
Minor Planets ◽  
The Sun ◽  
Physical Difference ◽  
Short Period ◽  
The One

There has long been speculation as to whether comets evolve into asteroidal objects. On the one hand, in the original version of the Oort (1950) hypothesis, the cometary cloud was supposed to have formed initially from the same material that produced the minor planets; and an obvious corollary was that the main physical difference between comets and minor planets would be that the latter had long since lost their icy surfaces on account of persistent exposure to strong solar radiation (Öpik, 1963). However, following a suggestion by Kuiper (1951), it is now quite widely believed that, whereas the terrestrial planets and minor planets condensed in the inner regions of the primordial solar nebula, icy objects such as comets would have formed more naturally in the outer parts, perhaps even beyond the orbit of Neptune (Cameron, 1962; Whipple, 1964a). Furthermore, recent studies of the evolution of the short-period comets indicate that it is not possible to produce the observed orbital distribution from the Oort cloud, even when multiple encounters with Jupiter are considered (Havnes, 1970). We must now seriously entertain the possibility that most of the short-period orbits evolved directly from low-inclination, low-eccentricity orbits with perihelia initially in the region between, say, the orbits of Saturn and Neptune, and that these comets have never been in the traditional cloud at great distances from the Sun.

3. Note on Solar Radiation

1888 ◽  
Vol 14 ◽  
pp. 118-121
Author(s):  
John Aitken
Keyword(s):  
Solar Radiation ◽  
The Sun ◽  
Geological History ◽  
Conservation Of Energy ◽  
Vast Amount ◽  
Chemical Theory ◽  
Energy Theory ◽  
The Many ◽  
Different Sources

In the many theories that have been advanced to explain the comparative constancy of solar radiation in long past ages as evidenced by geological history, it has been generally assumed that the temperature of the sun has not varied much, and to account for its not falling in temperature a number of theories have been advanced, all suggesting different sources from which it may have received the energy which it radiates as heat. Since the chemical theory was shown to be insufficient to account for the vast amount of heat radiated, other theories, such as the meteoric theory and the conservation of energy theory, have been advanced.

Sign in / Sign up

Export Citation Format

Share Document