Cloud dark matter

Fig. 11.15. Conditions for gas loss from a galaxy, as a function of gas mass Mg and the ratio < > of dark matter to baryons (stars + gas), assuming an energy input of 1038 erg s-1 and maximum dissipation from cloud-cloud collisions. PSS denotes the relation between < > and Mg deduced from observation by Persic, Salucci and Stel (1996). After Ferrara and Tolstoy (2000).

Spectral analysis shows quite clearly that the various types of atoms are exactly the same on Earth as in the sky, in my own hand or in the hand of Orion. Stars are material objects, in the baryonic sense of the term. All astrophysical objects, apart from a noteworthy fraction of the dark-matter haloes, all stars and gaseous clouds are undoubtedly composed of atoms. However, the relative proportions of these atoms vary from one place to another. The term abundance is traditionally used to describe the quantity of a particular element relative to the quantity of hydrogen. Apart from this purely astronomical definition, the global criterion of metallicity has been defined with a view to chemical differentiation of various media. Astronomers abuse the term metaT by applying it to all elements heavier than helium. They reserve the letter Z for the mass fraction of elements above helium in a given sample, i.e. the percentage of metals by mass contained in 1 g of the matter under consideration. (Note that the same symbol is used for the atomic number, i.e. the number of protons in the nucleus. The context should distinguish which is intended.)... 

The idea of dark matter was first mooted to resolve Zwicky s paradox, which relates to different estimates of galactic mass, based on luminosity and rotational models respectively. Rotational analysis consistently predicts excess mass, compared to the total luminous mass within the assumed limiting size of a galaxy, as defined by its so-called Holmberg radius. The subsequent discovery of massive clouds of both atomic and molecular hydrogen around typical galaxies and clusters may well account for this missing mass. 

The dark clouds were responsible for the discovery of ISM, as they absorb the light from stars which lies behind these clouds of interstellar matter. It is difficult to obtain reliable information on the dust particles. They are probably about 0.1 pm in diameter, consisting of a silicate nucleus and an envelope of compounds containing the elements C, O and N, which, with H and He, are the main elements present in interstellar space. There are only two sources of information for more exact characterisation of the dust particles ... 

The first extreme was that cloud or darkness whereof we have spoken formerly. Some call it the remote matter and the invisible chaos, but very improperly, for it is not invisible. This is the Jewish Ain-Soph outwardly, and it is the same with that Orphic night O Night, thou black nurse of the golden stars. Out of this darkness all things that are in this world came, as out of their fountain or matrix.3... 

However, according to the latest estimates, the fraction of our Galaxy s dark halo that could be explained by baryonic matter (low-luminosity stars and non-luminous compact, massive objects) cannot exceed 20%. These estimates are based on the effect such objects would have on the hght from stars in the Magellanic Clouds. It is concluded that the halo of our Galaxy, and probably that of other spirals of this type, is not principally made up of ordinary, atomic matter. 

Random turbulent process or other small perturbations in the field lead to local potential wells where the ISM can condense, pulling the magnetic field with it, and leading to a Rayleigh-Taylor (or runaway) instability. It is thought that this provides the initial mechanism for the formation of dark clouds of interstellar matter. 

First of all, volcanic activity must be mentioned it introduces both gases (see Section 2.3 and Subsection 3.6.2) and particles into the atmosphere. The particles play an important temporary role in the control of atmospheric optical properties and radiation balance. Thus, after the eruption of Krakatoa in 1883 unusual darkness was observed over Batavia and the height of the volcanic cloud reached the altitude of nearly 30 km (18 miles). After the violent eruption of the Agung volcano in 1963 the optical effect of ash particles was identified at several points of the Earth and a temperature increase of 2 C was measured in the stratosphere (see Cadle, 1973)due to the radiation absorption of particles. While an important part of volcanic particulate matter consists of dispersed lava, sulfuric acid also was detected in volcanic fume (Cadle, 1973). 

Th is Dark Power brings us inner confusion, and takes away the judgment of Good and Evil, Just and Unjust, Beautiful and Ugly, Good and Bad. Tn these realms all discernment is removed, piece by piece. This becomes more serious when it clouds our sense of the true and authentic in matters of religion. 

More commonly, a person s interest in matters of the spirit simply wanes with lack of attention. The individual may not even be aware of the loss, but he or she gradually realizes that there s no longer an animating or creative force in his or her life, bringing on a state of apathy or darkness, like living within a cloud. A person with a kapha disturbance like this may not feel despairing so much as lifeless—another form of depression. 

And know that the periods of the earth are in the water, which let it be as long as until thou puttest the same upon it. This matter being thus melted and burned, take the brain thereof and triturate it in most sharp vinegar, till it becomes obscured. This done, it lives in the putrefaction, let the dark clouds which were in it before it was killed be converted into its own body. Let this process be repeated, as I have described, let it again die, as I before said, and then it lives. 

Fig. 2.5 The horsehead nebula, a dark cloud illuminated on its right edge by FUV radiation from the nearby 09 star oOri. This edge is a template source for studying the physical and chemical processes in UV irradiated interstellar matter. The background image is taken in the visible at ESO. The small colour pictures show the distribution in various spectroscopic tracers [31]...

As for the matter whereof the Plants and Animals there consist , Huygens went on, we may venture to assert that their Growth and Nourishment proceeds from some liquid Principle. He suggested that the dark spots seen on the surface of Jupiter are likely to be clouds of condensed water vapour. Yet he added that I can t... 

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