Summary
This book, based on the 1964 paper by Antony Hewish, presents the foundational work on using interplanetary scintillation (IPS) to study radio sources. The central thesis is that the apparent broadening of a radio source's angular size when observed through the irregularities of the solar wind can be quantitatively analyzed to determine its true angular diameter. This technique, IPS, was pioneered as a method to measure the angular sizes of distant extragalactic radio sources that were otherwise too small to be resolved by contemporary radio telescopes.
The key ideas involve the scattering of radio waves by electron density fluctuations in the solar plasma and the correlation analysis of these fluctuations as observed from different locations or at different times. Readers learn how IPS can be used to infer the structure and distribution of radio sources, contributing significantly to early extragalactic astronomy and the understanding of cosmic radio emission. It established IPS as a crucial tool in radio astronomy for source characterization.
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Key concepts
- Interplanetary Scintillation (IPS) — The apparent fluctuation in the intensity of radio waves from distant sources as they pass through the solar wind.
- Angular Broadening — The increase in the apparent angular size of a radio source due to scattering by irregularities in the interplanetary medium.
- Spatial Structure of Radio Sources — The physical dimensions and distribution of emitting regions within distant celestial objects, measurable via IPS.
- Solar Wind Irregularities — Variations in electron density within the interplanetary plasma that cause the scattering of radio waves.