90
that led to the temporary exile of the Jesuit order, Secchi traveled to England, where
he worked in the observatory of Stonyhurst. Then he moved on to Georgetown
College near Washington D.C., where he taught physics. Motivated by his American
colleagues and mentors, Secchi began to study interesting features in the solar
atmosphere, such as the structure and temporal variance of sunspots, solar granulation, the photosphere and chromosphere, and later also the solar corona. Secchi was
one of the first astrophysicists to suggest that the solar core is in a gaseous state,
with the temperature steadily decreasing from the center to the surface.
During the 1860 eclipse of the Sun, Secchi participated in an expedition to the
“Desierto de las Palmas,” near Castellón de la Plana, in Spain, where he photographed solar prominences that at that time were only examinable during such
eclipses. Thanks to the comparison of these photographs with those taken by Warren
de la Rue in a very distant station, he provided the first conclusive demonstration
that these prominences are features belonging to the Sun. On the occasion of that
eclipse, he also became one of the first scientists to succeed in photographing the
solar corona (Fig. 5.5), turning him into a pioneer of scientific photography.
15
Ten
years earlier, during the eclipse of 1851, Secchi also tried to take a daguerreotype of
the eclipsed Sun, one of the first worldwide, but with poor results.
16
Secchi kept a daily record of the numbers of sunspots, their appearance, and
movement. He drew pictures of the most interesting spots at the eyepiece of his
telescope. When in 1868 Pierre J.C. Janssen and Joseph N. Lockyer discovered a
method for observing prominences on the fringes of a solar eclipse by focusing the
slit of the spectroscope on the range just beyond the bright solar disk, Secchi immediately used this new technique to observe within a limited wavelength range areas
of the uneclipsed Sun. He then continued to study these solar features intensely,
both visually and spectroscopically. Secchi also established the connection between
prominences and sunspots. Magnificent drawings of the huge red hydrogen jets
extending from the solar surface in stupendous and ever-changing shapes, published
in Secchi’s books, have become classics of astronomical literature and prime examples of superb scientific illustration (see Figs. 5.6 and 5.7).
Chinnici about the disciplinary status, which I think spectroscopy never achieved; see Hentschel
2002c for a detailed analysis.
15 On pioneers of astronomical photography, see e.g., Hoffleit 1950. In one of the recent articles
celebrating Secchi’s 200th birthday, he was even called “Fotograf der Sonne” cf. Christ in der
Gegenwart
23/2018,
online
available
at
https://www.herder.de/cig/cig-ausgaben/
archiv/2018/23-2018/der-fotograf-der-sonne/
16 The earliest daguerreotypes and photographs of the Sun, an extremely bright motif and thus very
difficult to photograph with any surface detail, were taken in 1845 by French physicists Louis
Fizeau (1819–1896) and Léon Foucault (1819–1868). Also see Darius 1984: 16, 20f., 40f. and
Hentschel 2002b on John William Draper’s first daguerreotype of the Moon, taken in 1840 with a
13 cm reflector of long focal length and an exposure time of 20 min.
K. Hentschel
that led to the temporary exile of the Jesuit order, Secchi traveled to England, where
he worked in the observatory of Stonyhurst. Then he moved on to Georgetown
College near Washington D.C., where he taught physics. Motivated by his American
colleagues and mentors, Secchi began to study interesting features in the solar
atmosphere, such as the structure and temporal variance of sunspots, solar granulation, the photosphere and chromosphere, and later also the solar corona. Secchi was
one of the first astrophysicists to suggest that the solar core is in a gaseous state,
with the temperature steadily decreasing from the center to the surface.
During the 1860 eclipse of the Sun, Secchi participated in an expedition to the
“Desierto de las Palmas,” near Castellón de la Plana, in Spain, where he photographed solar prominences that at that time were only examinable during such
eclipses. Thanks to the comparison of these photographs with those taken by Warren
de la Rue in a very distant station, he provided the first conclusive demonstration
that these prominences are features belonging to the Sun. On the occasion of that
eclipse, he also became one of the first scientists to succeed in photographing the
solar corona (Fig. 5.5), turning him into a pioneer of scientific photography.
15
Ten
years earlier, during the eclipse of 1851, Secchi also tried to take a daguerreotype of
the eclipsed Sun, one of the first worldwide, but with poor results.
16
Secchi kept a daily record of the numbers of sunspots, their appearance, and
movement. He drew pictures of the most interesting spots at the eyepiece of his
telescope. When in 1868 Pierre J.C. Janssen and Joseph N. Lockyer discovered a
method for observing prominences on the fringes of a solar eclipse by focusing the
slit of the spectroscope on the range just beyond the bright solar disk, Secchi immediately used this new technique to observe within a limited wavelength range areas
of the uneclipsed Sun. He then continued to study these solar features intensely,
both visually and spectroscopically. Secchi also established the connection between
prominences and sunspots. Magnificent drawings of the huge red hydrogen jets
extending from the solar surface in stupendous and ever-changing shapes, published
in Secchi’s books, have become classics of astronomical literature and prime examples of superb scientific illustration (see Figs. 5.6 and 5.7).
Chinnici about the disciplinary status, which I think spectroscopy never achieved; see Hentschel
2002c for a detailed analysis.
15 On pioneers of astronomical photography, see e.g., Hoffleit 1950. In one of the recent articles
celebrating Secchi’s 200th birthday, he was even called “Fotograf der Sonne” cf. Christ in der
Gegenwart
23/2018,
online
available
at
https://www.herder.de/cig/cig-ausgaben/
archiv/2018/23-2018/der-fotograf-der-sonne/
16 The earliest daguerreotypes and photographs of the Sun, an extremely bright motif and thus very
difficult to photograph with any surface detail, were taken in 1845 by French physicists Louis
Fizeau (1819–1896) and Léon Foucault (1819–1868). Also see Darius 1984: 16, 20f., 40f. and
Hentschel 2002b on John William Draper’s first daguerreotype of the Moon, taken in 1840 with a
13 cm reflector of long focal length and an exposure time of 20 min.
K. Hentschel