97
When Secchi and his assistants started to map these fascinating features on or
near the solar surface, their chemical composition was already known. The prominences appeared to be ejections from the solar surface at enormous speeds and in
enormous quantities in the form of hugh jets (sometimes 100,000 km long, 5000 km
wide, and reaching heights of up to 40,000 km). They emerged from a finer layer of
matter all around the Sun, the chromosphere. This chromosphere formed the background of the much more intensely shining prominences. When the observers
directed their spectroscopes to the rim of the Sun during the few moments of the
solar eclipse of 1868, they noticed a discontinuous spectrum with a few strong
hydrogen lines. This meant that gaseous hydrogen was certainly a strong component of the matter that was being expelled from the Sun’s surface in these prominences and in the solar chromosphere. The invention of the prominence spectroscope
(also called telespectroscope
18
by Giuseppe Lorenzoni) allowed astronomers to
observe these fascinating and temporally rapidly changing features in the monochromatic light of hydrogen’s red Hα line.
In the end, Secchi was not content with high-quality black-and-white etchings
and lithographs as were printed in the first, French edition of his classic textbook on
the Sun. The expanded and updated German version, which appeared in 1872 and
which included his latest observations up to the summer of 1871, was more elaborately illustrated. The Braunschweig publisher Westermann—actually a specialist
in high-quality geographic, geological, and meteorological maps—invested in chromolithographed plates made by the superb lithographer Albert Schütze in Berlin
(Fig. 5.8).
19
A controversy developed around how to interpret the fine structure (now called
granulation) visible under good seeing conditions in the photosphere, especially
near the penumbra of sunspots. In 1860, the engineer and amateur astronomer James
Hall Nasmyth (1808–1890), who later became famous for his three-dimensional
plaster models of the lunar surface, observed “peculiar features in the structure of
the Sun’s surface,” particularly along the borders of sunspots and during times of
extraordinarily good seeing.
20
A great debate ensued about whether these filaments
(mostly oblong in shape) were actually present, and if so, what object on Earth was
most similar to them: did they look like interlacing “willow leaves in an ocean of
fire,” randomly scattered, as Nasmyth argued, or like “rice grains,” as Stone and his
assistants at the Greenwich Observatory saw them? Were they “pores,” as William
work/padua-observations-of-solar-prominences-made-at-palermo-astronomical-observatoryby-tacchini/?lang=en
19 On Albert Schütze (1827–1908), see my Database of Scientific Illustration 1450–1905 (DSI):
http://www.uni-stuttgart.de/hi/gnt/dsi2/index.php?table_name=dsi&function=details&where_
field=id&where_value=593. Secchi’s chromolithographic plates became the high standard for
later reproductions (e.g., in the 4th ed. of Meyers Konversations-Lexikon (1885–1892) and competing textbooks such as in Schellen’s from 1872; see one of the first plates on the Sun, online at
https://upload.wikimedia.org/wikipedia/commons/a/aa/Meyers_b15_s0020a.jpg)
20 On the following see Bartholomew 1976, Meadows 1972, exp. ed. 2008: 315–321, chap. II and
postscript, and Hentschel 1999: 21–25.
5 Angelo Secchi, Stellar Spectroscopy, Solar Physics, and Visual Science Culture
When Secchi and his assistants started to map these fascinating features on or
near the solar surface, their chemical composition was already known. The prominences appeared to be ejections from the solar surface at enormous speeds and in
enormous quantities in the form of hugh jets (sometimes 100,000 km long, 5000 km
wide, and reaching heights of up to 40,000 km). They emerged from a finer layer of
matter all around the Sun, the chromosphere. This chromosphere formed the background of the much more intensely shining prominences. When the observers
directed their spectroscopes to the rim of the Sun during the few moments of the
solar eclipse of 1868, they noticed a discontinuous spectrum with a few strong
hydrogen lines. This meant that gaseous hydrogen was certainly a strong component of the matter that was being expelled from the Sun’s surface in these prominences and in the solar chromosphere. The invention of the prominence spectroscope
(also called telespectroscope
18
by Giuseppe Lorenzoni) allowed astronomers to
observe these fascinating and temporally rapidly changing features in the monochromatic light of hydrogen’s red Hα line.
In the end, Secchi was not content with high-quality black-and-white etchings
and lithographs as were printed in the first, French edition of his classic textbook on
the Sun. The expanded and updated German version, which appeared in 1872 and
which included his latest observations up to the summer of 1871, was more elaborately illustrated. The Braunschweig publisher Westermann—actually a specialist
in high-quality geographic, geological, and meteorological maps—invested in chromolithographed plates made by the superb lithographer Albert Schütze in Berlin
(Fig. 5.8).
19
A controversy developed around how to interpret the fine structure (now called
granulation) visible under good seeing conditions in the photosphere, especially
near the penumbra of sunspots. In 1860, the engineer and amateur astronomer James
Hall Nasmyth (1808–1890), who later became famous for his three-dimensional
plaster models of the lunar surface, observed “peculiar features in the structure of
the Sun’s surface,” particularly along the borders of sunspots and during times of
extraordinarily good seeing.
20
A great debate ensued about whether these filaments
(mostly oblong in shape) were actually present, and if so, what object on Earth was
most similar to them: did they look like interlacing “willow leaves in an ocean of
fire,” randomly scattered, as Nasmyth argued, or like “rice grains,” as Stone and his
assistants at the Greenwich Observatory saw them? Were they “pores,” as William
work/padua-observations-of-solar-prominences-made-at-palermo-astronomical-observatoryby-tacchini/?lang=en
19 On Albert Schütze (1827–1908), see my Database of Scientific Illustration 1450–1905 (DSI):
http://www.uni-stuttgart.de/hi/gnt/dsi2/index.php?table_name=dsi&function=details&where_
field=id&where_value=593. Secchi’s chromolithographic plates became the high standard for
later reproductions (e.g., in the 4th ed. of Meyers Konversations-Lexikon (1885–1892) and competing textbooks such as in Schellen’s from 1872; see one of the first plates on the Sun, online at
https://upload.wikimedia.org/wikipedia/commons/a/aa/Meyers_b15_s0020a.jpg)
20 On the following see Bartholomew 1976, Meadows 1972, exp. ed. 2008: 315–321, chap. II and
postscript, and Hentschel 1999: 21–25.
5 Angelo Secchi, Stellar Spectroscopy, Solar Physics, and Visual Science Culture