192
9 Mount Wilson
showed that the distances of star clusters in the Milky Way, as determined by
apparent magnitude and using spectral types, resulted in values for the diameter
(in parsec) of those clusters that systematically decreased with distance from
the Sun. The diameter from colors is affected by extinction and that from
spectral types is not. So there had to be extinction, and from that moment on
everyone was convinced of that too. Of course, it then also became clear that
the dust responsible for the extinction is concentrated in a very thin layer in
the Milky Way. Kapteyn never included extinction anymore in his studies after
1916; Shapley’s argument was sufficiently convincing. And not just for him;
it was universally accepted.
9.6 The Solar Union Congress, 1910
During the stay of the Kapteyns on Mount Wilson in 1910, a large meeting was
held of the International Union for the Cooperation in Solar Research. There
was a lot of interest, partly because astronomers from all over the United States
and Europe wanted to see the giant telescope and the enormous solar towers.
Although it was a congress on solar research, Hale was actually planning to
talk about coordinating solar research with that of stars, so the congress was an
incentive to bring the two areas of research together. There were participants
from both areas, with the result that most of the top astronomers from both
America and Europe were present, as well as the directors of virtually all the
influential observatories on both continents.
From the American institutes were in attendance Edward Pickering of Harvard, Edwin Frost of Yerkes Observatory, William Wallace Campbell (1862–
1938) from Lick Observatory (not far from San Francisco), Frank Schlesinger
(1871–1943) from the Allegheny Observatory (Pittsburgh), later director
of Yale Observatory (New Haven, Connecticut), Edward Emerson Barnard
(1857–1923) from Yerkes, Vesto Melvin Slipher (1875–1969) from Lowell
Observatory near Flagstaff, Arizona, Henry Norris Russell—known from the
Hertzsprung–Russell diagram—from Princeton (where he was to become director in 1912), Armin Otto Leuschner (1868–1953) from Berkeley. In fact,
without exception, these were leading astronomers and astrophysicists, who
investigated stars and nebulae and had little to do directly with solar research.
European participants were Frank Watson Dyson (1868–1939) then Astronomer Royal for Scotland, not long afterwards director of the Royal Greenwich Observatory, Jöns Oskar Backlund from Pulkovo near St. Petersburg,
Herbert Hall Turner from Oxford, Karl Schwarzschild of the Sternwarte
Göttingen, Johannes Robert Rydberg (1854–1919) of Lund Observatory in
9 Mount Wilson
showed that the distances of star clusters in the Milky Way, as determined by
apparent magnitude and using spectral types, resulted in values for the diameter
(in parsec) of those clusters that systematically decreased with distance from
the Sun. The diameter from colors is affected by extinction and that from
spectral types is not. So there had to be extinction, and from that moment on
everyone was convinced of that too. Of course, it then also became clear that
the dust responsible for the extinction is concentrated in a very thin layer in
the Milky Way. Kapteyn never included extinction anymore in his studies after
1916; Shapley’s argument was sufficiently convincing. And not just for him;
it was universally accepted.
9.6 The Solar Union Congress, 1910
During the stay of the Kapteyns on Mount Wilson in 1910, a large meeting was
held of the International Union for the Cooperation in Solar Research. There
was a lot of interest, partly because astronomers from all over the United States
and Europe wanted to see the giant telescope and the enormous solar towers.
Although it was a congress on solar research, Hale was actually planning to
talk about coordinating solar research with that of stars, so the congress was an
incentive to bring the two areas of research together. There were participants
from both areas, with the result that most of the top astronomers from both
America and Europe were present, as well as the directors of virtually all the
influential observatories on both continents.
From the American institutes were in attendance Edward Pickering of Harvard, Edwin Frost of Yerkes Observatory, William Wallace Campbell (1862–
1938) from Lick Observatory (not far from San Francisco), Frank Schlesinger
(1871–1943) from the Allegheny Observatory (Pittsburgh), later director
of Yale Observatory (New Haven, Connecticut), Edward Emerson Barnard
(1857–1923) from Yerkes, Vesto Melvin Slipher (1875–1969) from Lowell
Observatory near Flagstaff, Arizona, Henry Norris Russell—known from the
Hertzsprung–Russell diagram—from Princeton (where he was to become director in 1912), Armin Otto Leuschner (1868–1953) from Berkeley. In fact,
without exception, these were leading astronomers and astrophysicists, who
investigated stars and nebulae and had little to do directly with solar research.
European participants were Frank Watson Dyson (1868–1939) then Astronomer Royal for Scotland, not long afterwards director of the Royal Greenwich Observatory, Jöns Oskar Backlund from Pulkovo near St. Petersburg,
Herbert Hall Turner from Oxford, Karl Schwarzschild of the Sternwarte
Göttingen, Johannes Robert Rydberg (1854–1919) of Lund Observatory in