The Trouvelot astronomical drawings manualTrouvelot, E. L. (Etienne Leopold)
Science
The Trouvelot astronomical drawings manual
Trouvelot, E. L. (Etienne Leopold)
Astronomy -- Pictorial works
Seen with the naked eye, Saturn shines in the night like a star of the
first magnitude, whose dull, soft whiteness is, however, far from
attaining the brilliancy of Venus or Jupiter, although it sometimes
approaches Mars in brightness. Saturn hardly ever exhibits the
phenomenon of scintillation, or twinkling, a peculiarity which makes it
easily distinguishable among the stars and planets of the heavens.
The synodical period of Saturn occupies 1 year and 13 days, so that
every 378 days, on an average, this planet holds the same position in
the sky relatively to the Sun and the Earth.
The mean distance of Saturn from the Sun is a little over 9½ times that
of our globe, or 872,000,000 miles. Owing to the orbital eccentricity,
this distance may increase to 921,000,000 miles, when the planet is in
aphelion; or decrease to 823,000,000 miles, when it is in perihelion;
Saturn being therefore 98,000,000 miles nearer to the Sun when in
perihelion than in aphelion. If gravitation were free to exert its
influence alone, Saturn would fall into the Sun in 5 years and 2 months.
The distance of Saturn from the Earth varies, according to the position
of the two planets in their respective orbits. At the time of
opposition, when the Earth lies between the Sun and Saturn, this
distance is smallest; while, on the contrary, at the time of
conjunction, when the Sun lies between the Earth and Saturn, it is
greatest. Owing, however, to the eccentricity of the orbits of Saturn
and our globe, and the inclination of their planes to each other, and
owing also to the variable heliocentric longitude of the perihelion, the
distance of the two planets from each other at their successive
conjunctions and oppositions is rendered extremely variable. At present
it is when the oppositions of Saturn occur in December that this planet
comes nearest to us; while when the conjunctions take place in June, the
distance of Saturn from the Earth is the greatest possible. In the
former case the distance of the planet from our globe is only
730,000,000 miles; while in the last it is 1,014,000,000 miles, the
difference between the nearest and farthest points of Saturn's approach
to us being no less than 284,000,000 miles, or over three times the mean
distance of the Sun from the Earth.
From the great variations in the distance of Saturn from the Earth,
necessarily result corresponding changes in the brightness and apparent
diameter of this body. When it is farthest from us, its angular diameter
measures but 14"; while, when it is nearest, it measures 20".
The orbit of Saturn is inclined 2°30' to the ecliptic, and its
eccentricity, which equals 0,056, is over three times that of the
Earth's orbit.
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