On the telescopic disks of stars - a review and analysis of stellar observations from the early 17th through the middle 19th centuries

TL;DR

This paper reviews historical telescopic star observations from the 17th to 19th centuries, analyzing how Airy's theory explains these observations and highlighting their validity despite modern misconceptions.

Contribution

It provides a comprehensive analysis linking historical star disk observations with Airy's theoretical explanation, emphasizing their continued relevance.

Findings

Airy's theory accounts for historical star disk observations.

Historical observations are valid and merit further study.

Modern views on star disks are inconsistent with historical data.

Abstract

Since the dawn of telescopic astronomy astronomers have observed and measured the "spurious" telescopic disks of stars, generally reporting that brighter stars have larger disks than fainter stars. Early observers such as Galileo Galilei interpreted these disks as being the physical bodies of stars; later observers such as William Herschel understood them to be spurious; some, such as Christian Huygens, argued that stars show no disks at all. In the early 19th century George B. Airy produced a theoretical explanation of star images sufficient to explain all historical observations, but astronomers were slow to fully recognize this. Even today conventional wisdom concerning stars and telescopes stands at odds to both historical observations and Airy's theory. We give a detailed analysis of both historical observations and Airy's theory, illustrating how Airy's theory explains the historical observations, from Galileo to Huygens to Herschel. We argue that the observations themselves appear in all cases to be valid and worth further study.