Problems in astrophysics

Metadata

Gutenberg ID

79177

Title

Problems in astrophysics

Language

en

Book source

Project Gutenberg

Description max 80 words

A pioneering 1903 astrophysics text by Agnes M. Clerke, this work dedicates itself to Sir David Gill and explores the chromospheric spectrum, stellar variability, and the composition of solar prominences through early 20th-century spectroscopic discoveries.

Summary up to 500 words

In her seminal 1903 text, *Problems in Astrophysics*, Agnes M. Clerke investigates the complex physics of the Sun and variable stars, serving as a crucial bridge between terrestrial physics and astrophysical inquiry. The work is rich with contemporary observational data and illustrations, challenging existing theories regarding elemental distribution and stellar behavior. Clerke begins by analyzing the chromospheric spectrum, which she describes as almost purely discontinuous, composed of detached bright lines. She details the identification of permanent radiations belonging to hydrogen, helium, and calcium. A significant portion of her analysis focuses on the peculiar behavior of helium series in solar prominences. While laboratory experiments show helium series are inseparable, Clerke notes that in the Sun, the 'yellow' helium is always present, whereas the 'green' set appears only about one-fourth as often. She examines the anomalous levitation of calcium, which floats as high as hydrogen despite its greater density, suggesting an inexplicable property or perhaps electrolytic action. Furthermore, she highlights the presence of other metals like titanium, scandium, chromium, manganese, and carbon in the solar envelope. The discovery of titanium and carbon vapors, which defy expected gravitational sorting, indicates that influences beyond simple gravity regulate elemental distribution near the Sun. The text further analyzes peculiar and irregular variable stars, distinguishing between two primary categories. Stars with short periods are often close pairs where circulation laws prescribe light changes, whereas Mira-type variables, such as U Geminorum and S 2 Cygni, exhibit marked irregularity driven by internal disturbances. Through detailed light-curves, Clerke demonstrates that stellar variability stems from cyclical changes in vertical circulation and internal energy. She draws strong parallels between solar spot cycles and stellar light changes, noting that light maxima in stars correspond to spot maxima in the Sun. In both cases, a development of internal energy enhances incandescence, sometimes accompanied by rendings of the photospheric envelope. Clerke addresses the perplexing optical phenomena of certain variables, such as V Cygni, which appears diffuse and nebulosities at low minima but sharp and precise at others. While some of these effects may be attributed to atmospheric or instrumental causes, she argues that genuine physical alterations in the stars' luminous quality also occur. She concludes that the cyclical variations of these bodies depend essentially on the rise and fall of activity in vertical circulation. By comparing the dissymmetry of solar and stellar disturbance curves, she establishes that the phenomena differ in degree rather than in kind, providing an irrefragable proof of the correspondence between solar and stellar epochs.

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4.2/5

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Categories

• Science