WWW.ASTRONOMY.COM 15
in the second half of the 19th
century and spiked to 48 percent
in the 20th century.
The researchers also discov-
ered discrepancies over what
constitutes the color violet. For
instance, the color beyond blue
on the spectrum is called purple
in the U.S., but violet in the U.K.;
alternatively, reddish-purple is
sometimes called violet in the
U.S., but hardly ever so in the
U.K. This led Tager and his col-
leagues to create the first working
definition for the color violet: “all
mixtures of red and blue for
which blue dominates.”
Introducing violet
In his 1864 book Sidereal
Chromatics (On the Colours of
Multiple Stars), Smyth recognizes an evolution not just
in art but also in the color perception of skywatchers.
“ T he a nc ient s recog n i sed no blue st a rs ,” he s ay s. “ T he y
only spoke of white or red ones.” Blue stars, he notes,
were not introduced into the astronomical lexicon until
French physicist Edme Mariotte first men-
tioned them in 1686. Smyth also notes that
“although single red stars are frequently met
with, there is not an instance of a solitary
green, purple, blue, or violet-coloured one
being found.”
However, Smyth did note the appearance
of violet in double stars. In fact, he appears
to be the first telescopic observer to use the
color violet in his descriptions of stars. For
instance, as early as the 1830s, he recorded
numerous double stars with white or yellow
primaries and a violet secondary. To my
knowledge, all observers before him stuck to
the traditional color schemes in their
descriptions of double stars. Observers fol-
lowing Smyth, however, began incorporating violet into
their double star vocabulary, albeit sparingly.
Inspired by science
In their March 2021 paper, Tager and his colleagues
describe how contemporary developments in color
theory and their adoption by Impressionist painters
may naturally have led to an increase in the use of violet
from 1863 onwards.
Interestingly, in the early years of the Impressionist
movement, we see Smyth promoting in his Sidereal
Chromatics “t he laws of ha rmonious a l lia nce a nd con-
trast of colour — that yellow is of all hues the nearest
related to light, and its complementary violet or purple
to darkness.” The above quote seems to indicate that
Smyth was familiar with Goethe’s analysis of the sen-
sory and psychological effects induced by different
colors, which he published in his
1810 work Theory of Colors.
Smyth then goes on to say,
“Many of the observed tints of
stellar companions would of
course turn out to be merely
complementary [colors] and
caused by the law of simultane-
ous contrast.” This concept,
introduced by French chemist
Michel Eugène Chevreul (and
inspired by Goethe) in his 1839
The Principles of Harmony and
Contrast of Colours, blossomed
around the time that Smyth was
making his color observations,
some 25 years before he pub-
lished Sidereal Chromatics.
Chevreul’s law stated that
when two adjacent colors are
observed, their perceived colors
shift toward the complementary color of the adjacent
color. For a binary star that contains a bright, slightly
orange-yellow star next to a white star, Chevreul’s law
predicts that the human eye will see the color of that
white star shifted toward violet. That’s because violet
is the complementary color to yellow, as
they are opposing hues on a color
wheel. These inferences suggest
that science theory had begun
to make its mark on visual
telescopic observations by
the mid-19th century.
And it was this type of
optical effect (simultane-
ous contrast for colors) that
the Impressionists sought
to capture and exploit in
their works. This allowed them
to create even stronger color
contrasts — a canvas bristling with
scientific proof that what the eye perceived
and the brain understood were two different things.
“I mpre s sion i st pa i nters u sed t he colou r v iolet so prol i f i-
cally,” Tager wrote for Psyche, “that critics accused
them of violettomania.”
While the range of colors of stars are limited to hues
that vary from reddish orange to pale blue, what our
eye-brain system sees depends on many factors. These
include atmospheric clarity, the telescope used, con-
trast, and bias (from knowledge of a star’s spectral class
and color temperature), among others. But don’t let that
stop you from recording what you see rather than what
you are expected to see.
And as always, report what you see or don’t see to
[email protected].Smyth
appears to
be the first
telescopic
observer to
use the color
violet in his
descriptions
of stars.
BROWSE THE “SECRET SKY” ARCHIVE AT
http://www.Astronomy.com/OMearaLEFT: William Henry
Smyth presented this
color scheme for
double stars in his
Sidereal Chromatics.
“Where the mental
impression is not
quite adequately
represented by these
tints,” he said, “it can
be modified by an
expressive adjective.”
The shades from
white to pale yellow
were so numerous, he
excluded them from
the chart. Violet and
lilac would be
registered under
“purple.” COURTESY OF
STEPHEN JAMES O’MEARABELOW: The double
star Albireo’s primary
has a spectral type of
K2, emitting an
yellowish-orange
glow; the secondary
is B8 — nearly pure
white. But due to
complementary
colors, the secondary
often takes on a
brilliant blue hue.
KFIR SIMON