Astronomical observations

The Big Bang Theory is the prevailing theory of the origin of the universe, and it is based on astronomical observations. According to this theory, about 15 billion years ago all the matter and energy in the visible universe was concentrated in a small, hot, dense region, which flew apart in a gigantic explosion. 

Walker, G., Astronomical observations, Cambridge University Press, 1987... 

In astronomical observation, the probability of population is much smaller because the angular size of the thermal source is much smaller than the Airy spot of the instrument. Therefore we will consider the correlation of signals which are much smaller than the noise. Let us normalize the pump to unity. Each output gives a signal ... 

Much of the electromagnetic spectrum has been used to investigate the structure of matter in the laboratory but the atmospheric windows restrict astronomical observations from Earth. Irritating as this is for astronomers on the ground, the chemical structure of the atmosphere and the radiation that it traps is important to the origins of life on Earth. The light that does get through the atmosphere, however, when analysed with all of the tools of spectroscopy, tells the molecular story of chemistry in distant places around the Universe. 

Measurements in the laboratory are much more sensitive to spectral separations and hence understanding the spectrum of a molecule uniquely for the purposes of identification. However, the astronomical observations are limited by the telescope resolution and the atmospheric shimmer but the intrinsic information content of microwave spectra provides the best method for molecular identification - the other regions of the spectrum have their uses, as we shall see. 

Satellite astronomical observations remove the problems of the atmospheric absorption windows but require more sophisticated orbital spacecraft. Telescopes mounted on aircraft in part can achieve better results but state-of-the-art results are obtained from orbiting satellites. Probably the most successful satellite telescope for public... 

Astronomical observations are complicated by the presence of many molecules in the field of view so that the measured spectrum is a complicated mixture of allowed rotational transitions such as in the Orion nebula (Figure 3.11). Identifying molecules is then a matter of experience based on knowledge of absolute transition frequencies and how the lines form rotational progressions. There are many things to consider in assigning the spectrum ... 

The existence and distribution of the chemical elements and their isotopes is a consequence of nuclear processes that have taken place in the past in the Big Bang and subsequently in stars and in the interstellar medium (ISM) where they are still ongoing. These processes are studied theoretically, experimentally and obser-vationally. Theories of cosmology, stellar evolution and interstellar processes are involved, as are laboratory investigations of nuclear and particle physics, cosmo-chemical studies of elemental and isotopic abundances in the Earth and meteorites and astronomical observations of the physical nature and chemical composition of stars, galaxies and the interstellar medium. 

However, it is impossible to isolate the matter in the core of a neutron star for detailed study. It is thus necessary to identify observable aspects of neutron stars that can be, in some sense, mapped to the equation of state of high-density material. In this review we discuss various constraints on the equation of state from astronomical observations. We focus on observations of accreting binary systems. 

Then suddenly, against her will but in all lucidity, Urania the ancient Greek muse of astronomy was compelled to admit that what is visible is only the froth of existence. She even came to give precedence to what cannot be seen, to what neither shines nor absorbs light. Astronomical observation and theoretical reasoning suggest that most of matter is actually invisible. 

The value of the decay constant (1) must have remained constant over the age of the solar system and the galaxy, and it must be accurately known. As we discussed in Chapter 2, this third assumption is well founded for conditions relevant to cosmochemistry. The concordance of dates given by systems using a variety of decay paths and astronomical observations of decay rates of newly synthesized elements over billions of years provides strong evidence that the decay rates have remained constant. In addition, detailed experiments and theoretical models have identified the extreme conditions (e.g. centers of stars) under which this assumption breaks down for certain isotopes, thereby identifying the exceptions that prove the rule. (4) It must be possible to assign a realistic value to the initial abundance of the... 

Our general understanding of how the solar system came to be comes from a variety of different sources. Astronomical observations and theoretical modeling provide a broad picture of how stars form. Elemental and isotopic abundances in the solar system,... 

Hester, J. J. and Desch, S. J. (2005) Understanding our origins Star formation in HII region environments. In Chondrites and the Protoplanetary Disk, ASP Conference Series, 341, eds. Krot, A. N., Scott, E. R. D. and Reipurth, A. San Francisco Astronomical Society of the Pacific, pp. 107-130. A clear and up-to-date review of astronomical observations that constrain models for solar system formation. 

In a talk, very important even today, J. H. Oort discussed the Distribution of Galaxies and the Density of the Universe. Lovell presented Radio Astronomical Observations Which May Give Information on the Structure of the Universe. ... 

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