Letters on Astronomy: in which the Elements of the Science are Familiarly Explained in Connection with Biographical Sketches of the Most Eminent AstronomersOlmsted, Denison
Science
Letters on Astronomy: in which the Elements of the Science are Familiarly Explained in Connection with Biographical Sketches of the Most Eminent Astronomers
Olmsted, Denison
Astronomy
Figure 60, facing page 247, represents Saturn, as it appears to a
powerful telescope, surrounded by its rings, and having its body striped
with dark belts, somewhat similar, but broader and less strongly marked
than those of Jupiter. In telescopes of inferior power, but still
sufficient to see the ring distinctly, we should scarcely discern the
belts at all. We might, however, observe the shadow cast upon the ring
by the planet, (as seen in the figure on the right, on the upper side;)
and, in favorable situations of the planet, we might discern glimpses of
the shadow of the ring on the body of the planet, on the lower side
beneath the ring. To see the division of the ring and the satellites
requires a better telescope than is in possession of most observers.
With smaller telescopes, we may discover an oval figure of peculiar
appearance, which it would be difficult to interpret. Galileo, who first
saw it in the year 1610, recognised this peculiarity, but did not know
what it meant. Seeing something in the centre with two projecting arms,
one on each side, he concluded that the planet was triple-shaped. This
was, at the time, all he could learn respecting it, as the telescopes he
possessed were very humble, compared with those now used by astronomers.
The first constructed by him magnified but three times; his second,
eight times; and his best, only thirty times, which is no better than a
common ship-glass.
It was the practice of the astronomers of those days to give the first
intimation of a new discovery in a Latin verse, the letters of which
were transposed. This would enable them to claim priority, in case any
other person should contest the honor of the discovery, and at the same
time would afford opportunity to complete their observations, before
they published a full account of them. Accordingly, Galileo announced
the discovery of the singular appearance of Saturn under this disguise,
in a line which, when the transposed letters were restored to their
proper places, signified that he had observed, "that the most distant
planet is triple-formed."[13] He shortly afterwards, at the request of
his patron, the Emperor Rodolph, gave the solution, and added, "I have,
with great admiration, observed that Saturn is not a single star, but
three together, which, as it were, touch each other; they have no
relative motion, and are constituted of this form, oOo, the middle one
being somewhat larger than the two lateral ones. If we examine them with
an eyeglass which magnifies the surface less than one thousand times,
the three stars do not appear very distinctly, but Saturn has an oblong
appearance, like that of an olive, thus, {oblong symbol}. Now, I have
discovered a court for Jupiter, (alluding to his satellites,) and two
servants for this old man, (Saturn,) who aid his steps, and never quit
his side."
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