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3 Astronomy Around 1875
Fig. 3.8 The famous cross-section of Herschel’s Sidereal System based on his 20-foot
star counts (this is a smaller and earlier version of the 40-foot telescope in Fig. 3.7). The
point in the middle is the position of the Sun. From The Construction of the Heavens
(1785) [40]
of his life he was convinced that the Galaxy was flattened, as if it were
bounded by two planes, between which it stretched infinitely far. Herschel
was the first to attempt to derive an model of the spatial distribution of stars.
In summary, around the time that our main character, Jacobus Cornelius
Kapteyn, graduated from university in 1875, a great deal of knowledge about
the structure of the Solar System was already available to astronomers, but
the astronomy of the stars was still in the cataloging stage. Nothing was
known about the physical characteristics of stars, nor did astronomers know
anything about their structure, formation and evolution. Little could be said
about their spatial distribution; especially this last problem of the structure
of the Sidereal System would fascinate and occupy Kapteyn throughout his
life.