Probleme der Astronomie

Seeliger, Hugo von

Bibliographic data

Multivolume work

Persistent identifier:: 1670259072

Author:: Meyer, Hans

Title:: Lehrbuch der organisch-chemischen Methodik

Type of content:: Lehrbuch

Year of publication:: 1922

Place of publication:: Wien

Publisher of the original:: Verlag von Julius Springer

Identifier (digital):: 1670259072

Language:: German

Additional Notes:: Bände 1-3,2 erschienen von 1922-1940

Document type:: Multivolume work

Volume

Persistent identifier:: 1670273296

Author:: Meyer, Hans

Title:: Nachweis und Bestimmung organischer Verbindungen

Sub title:: mit 11 Abbildungen

Scope:: XII, 426 Seiten

Type of content:: Lehrbuch

DOI:: 10.14463/KXP:1670273296

Year of publication:: 1933

Place of publication:: Berlin

Publisher of the original:: Verlag von Julius Springer

Identifier (digital):: 1670273296

Illustration:: Illustrationen

Signature of the source:: a 368(2)

Language:: German

Usage licence:: Public Domain Mark 1.0

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Chemistry

Chapter

Title:: 41. n-Nonylalkohol.

Document type:: Multivolume work

Structure type:: Chapter

A. S. Eddington: 32 its intensity can be measured directly with the bolometer or more easily deduced from its luminous quality. The procedure may be reversed. From the observed intensity of the emitted radiation the unknown opacity of the stellar material can be found. Thus the data for Capella show that its opacity is about 120 C.G.S.units. This means that a screen of stellar material of thickness such as to contain xihrg m - P er sq.cm, would let through only 1 /e (e = 2 - 718 ) of the radiation falling on it. To illustrate the significance of this let us enter Capella and find a region where the density is equal to that of the atmosphere in which we live; a slab of the material only 5 cms. thick would form a screen so opaque that only of the radiation falling on one side of it would get through to the other side, the rest being absorbed in the material. It seems at first surprising that 5 cms. of gas could stop the aether-waves so effectually, but we might have anticipated something like this from our general physical knowledge. Different names are given to æther-waves according to their wave length. The longest are the Hertzian waves used in wireless telegraphy; then come the invisible heat waves, then light waves, then photographic or ultra-violet waves. Beyond these we have x-rays, and finally the y-rays emitted by radioactive substances. Where in this seiies are we to place the æther-waves in the interior of a star? It is solely a question of temperature, and at stellar temperatures the æther-waves are x-rays — more precisely, they are very “soft” x-rays. Now x-rays, and especially soft x-rays, are strongly absorbed by all substances. The opacity which we have found for Capella has about the usual value of the opacity of substances to x-rays measured in the laboratory. It is gratifying to be able to measure the absorption of x-rays inside a star and find a result similar to that obtained by physicists who experiment on terrestrial substances in the laboratory. It is of even greater interest if the stellar experiment turns out to be not a mere repetition but an extension of the laboratory experiments, so that the influence of conditions unattainable in terrestial surroundings may be traced. A careful examination shows that the correspondence be tween the stellar and the terrestrial absorption-coefficients is not so close as at first sight appeared. In the laboratory the absorption varies very rapidly according to the wave-length of the radiation that is being absorbed. By using stars of different temperatures we can also experi ment over a considerable range of wave-length, and the astronomical result is that the absorption is neaily independent of wave-length; we cannot yet detect with certainty whether it increases or decreases. Here is a striking contradiction. Further the laboratory results to which I have referred apply to radiation between 1 and 2 Angstrom units, whereas the radiation in Capella is in the main between 5 and 10 units. If we extrapolate the results for Capella according to the stellar law —

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