Topics in Modern Cosmology

2020 ◽  
pp. 361-684
Author(s):  
P. J. E. Peebles
Keyword(s):  
Spatial Distribution ◽  
Milky Way ◽  
Milky Way Galaxy ◽  
Statistical Estimates ◽  
Physical Universe ◽  
Luminous Galaxies ◽  
Modern Cosmology ◽  
Gas Cloud ◽  
Island Universes

This chapter recounts the discovery that the spiral nebulae are galaxies of stars and coequals of the Milky Way, which led to the exploration of a new level in the hierarchy of structure in the physical universe called the realm of the spiral nebulae. It details how cosmology has grown to include the study of other systems, such as the radiation backgrounds and the gas cloud, but common luminous galaxies comparable to the Milky Way remain the centerpiece. It also highlights some of the ways people came to see that the spiral nebulae as island universes of stars and discusses some elements of the systematics of the structures and spatial distribution of the galaxies. The chapter reviews the luminosity of the Milky Way galaxy that had been estimated from star counts and statistical estimates of star distances by 1920. It mentions Ernst Öpik, who put the ratio of the mass to luminosity.

Kant and extragalactic revolution in astronomy

2004 ◽  
Vol 47 (1-2) ◽  
pp. 95-109
Author(s):  
Milan Cirkovic
Keyword(s):  
History Of Astronomy ◽  
Physical Universe ◽  
History Of ◽  
Island Universes

In this paper we briefly consider the role Kant's early philosophy, and notably his "island universes" hypothesis played in the history of astronomy. There are many reasons for this, including the coincidence of Kant's jubilee year with 80 years since Hubble's discovery (1924) of the extragalactic universe. This discovery, confirming the "island universes" hypothesis revolutionized our picture of the physical universe. Prehistory of this revolution has another aspect, apart from the historical one, of significance for philosophy: it presents one of the best supported and empirically documented instances of the application of the Duhem-Quine thesis on subdetermination of theory by experiments.

The Long View of Planetary Systems

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Planetary Systems ◽  
Giant Planets ◽  
Milky Way Galaxy ◽  
Population Statistics ◽  
The Past ◽  
General Terms ◽  
The Galaxy ◽  
The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

scholarly journals A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Galaxies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 5
Author(s):  
Xiang Cai ◽  
Jonathan H. Jiang ◽  
Kristen A. Fahy ◽  
Yuk L. Yung
Keyword(s):  
Statistical Estimation ◽  
Milky Way ◽  
Galactic Center ◽  
Model Simulation ◽  
Temporal Variations ◽  
Extraterrestrial Intelligence ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
Peak Location ◽  
Intelligent Life

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

scholarly journals LIGHT SUPERCONDUCTING STRINGS IN THE GALAXY

2007 ◽  
Vol 16 (12b) ◽  
pp. 2399-2405 ◽  
Author(s):  
FRANCESC FERRER ◽  
TANMAY VACHASPATI
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Particle Physics ◽  
Milky Way ◽  
Gamma Ray ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Magnetic Field ◽  
The Galaxy ◽  
Intense Source

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.

Milky Way galaxy is fluttering like a flag

2013 ◽  
Vol 220 (2941) ◽  
pp. 18
Author(s):  
Michael Slezak
Keyword(s):  
Milky Way ◽  
Milky Way Galaxy

Computer Information Library Clusters

2019 ◽  
pp. 142-147
Author(s):  
Fu Yuhua
Keyword(s):  
Solar System ◽  
Social Science ◽  
Natural Science ◽  
Milky Way ◽  
Variation Principle ◽  
Unified Theory ◽  
Milky Way Galaxy ◽  
System Information ◽  
Set Up

Based on creating generalized and hybrid set and library with neutrosophy and quad-stage method, this chapter presents the concept of computer information library clusters (CILC). There are various ways and means to form CILC. For example, CILC can be considered as the “total-library” and consists of several “sub-libraries.” As another example, in CILC, a total-library can be set up, and a number of sub-libraries are side by side with the total-library. Specially, for CILC, the operation functions can be added; for example, according to natural science computer information library clusters (natural science CILC), and applying variation principle of library (or sub-library), partial and temporary unified theory of natural science so far with different degrees can be established. Referring to the concept of natural science CILC, the concepts of social science CILC, natural science and social science CILC, and the like can be presented. While referring to the concept of computer information library clusters, the concepts of computer and non-computer information library clusters, earth information library clusters, solar system information library clusters, Milky Way galaxy information library clusters, universe information library clusters, and the like can be presented.

Sign in / Sign up

Export Citation Format

Share Document