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The abundance of helium relative to hydrogen in the Orion Nebula

Citation

Mathis, John Samuel (1956) The abundance of helium relative to hydrogen in the Orion Nebula. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06072004-163340

Abstract

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Spectrograms were taken at two slit positions in the brighest portion of the Orion Nebula near the exciting star [...] Ori C. Four independent measurements were made in each slit position of the ratios of the He I lines [...], and [...] to the hydrogen lines H , H , and H , respectively. The ratios of the [OIII] lines [...] and [...] and of the [OII] lines [...] and [...] were also determined. Reddening by interstellar absorption was taken into account.

The electron density was found from the [OII] lines to be 3,800 [...]. The electron temperature was found from the [OIII] lines to be 10,000[degrees]K. The theory of statistical equilibrium was developed for neutral helium, and from the three helium lines the ratio of abundances of helium and hydrogen was found to be 0.128 by number. All three lines gave results within nineteen per cent of the average in both slit positions.

It was found that the absorption of the line of He I at [...] in the spectrum of [...] Ori, C could take place in only .025 parsec under the most favorable conditions.

In order to estimate the lifetime of the [...] level in helium the probability of two-photon emission was estimated. The estimate was [...].

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Osterbrock, Donald E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1956
Record Number:CaltechETD:etd-06072004-163340
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-06072004-163340
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2493
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:08 Jun 2004
Last Modified:26 Dec 2012 02:52

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