Once when
we pointed out to my Mother-in-Law the presence of Mars in the northern sky she
exclaimed. ‘Eee. Well I never knew Mars was up my road!’ I experienced a similar
revelation the other week myself when I deployed my telescope to the top patio
and aimed it just above the rooftop, which was helpfully hiding the bright
moon. As I pointed the scope at the bright object that my handy mobile app'
identified as the planet Saturn and twiddled the appropriate knobs to scan the
heavens, all at once the planet came unmistakably into view.
I caught
my breath. It was beautiful. I had not expected with my puny little 76mm
telescope that I would have had such a fine view of Saturn but there it was,
rings and all, shining brightly with its distinctive yellow hue. I could even make out one - no - two moons.
To be able to look upon that impossibly distant world with my own eyes moved me
more than I had known that it would. I still haven't tired of gazing at it as it shines brightly over my rooftop.
When
Galileo turned his telescope towards Saturn in July 1610 he found himself
greatly puzzled by its appearance. The limitations of his equipment meant that
Galileo was not able to observe the rings with clarity but instead beheld what
he described as a ‘planet triform’. Galileo supposed that Saturn was flanked by
two smaller moons which never altered in their positions relative to the larger
planet. Until such time as he could be confident of his findings, in a common
practice amongst enlightenment thinkers at the time, Galileo circulated his theory
in the form of an anagram. In the event that another astronomer came to the
same conclusion and published their findings before him, Galileo could provide
the solution to the anagram and reveal that he had been right all along! Two
years later however, when he observed Saturn again, the great scholar was
perturbed to find that the ‘moons’ had disappeared. Despite his puzzlement
Galileo confidently predicted that the moons would return and so in due course
they did. Indeed, as more curious observers turned their instruments towards
the heavens a bewildering array of manifestations of the planet Saturn were
described. What on earth were these strange phenomena?
Danish
lens maker and astronomer Christiaan Huygens, from whose 1659 publication Systema Saturnium the above diagram is
taken, was the first observer to finally be able to discern the truth of the
mystery when he deduced that the planet Saturn was surrounded by a ring. Huygens
was also the first to observe the moon Titan in orbit around Saturn. Huygens,
like Galileo, at first released his findings in the form of an anagram whilst
he continued his observations and firmed up his convictions regarding the
planet. The solution to the anagram as he revealed in Systema Saturnium was Annulo cingitur,
tenui, plano, nusquam cobaerente, ad eclipticam inclinator: It is encircled
by a ring, thin, plane, nowhere attached, inclined to the ecliptic.
Huygens
believed the ring to be a solid structure, although he was uncertain as to its
composition; merely ascribing its existence to the ‘power and majesty of nature’.
I believe that I
should digress here to meet the objection of those who will find it exceedingly
strange and possibly unreasonable that I should assign to one of the celestial
bodies a figure the like of which has up to this time not been found in any one
of them, although, on the other hand, it has been believed as certain, and
considered as established by natural law, that the spherical form is the only
one adapted to them; and that I should place this solid and permanent ring (for
such I consider it) about Saturn, without attaching it by any joints or ties,
although imagining that it preserves a uniform distance on every side and
revolves in company with Saturn at a very high rate of speed. These men should
consider that I do not construct this hypothesis from pure invention and out of
my own fancy, as the astronomers do their epicycles, which nowhere appear in
the heavens, but that I perceive this ring very plainly with the eyes; with
which, obviously, we discern the figures of all other things. And there is,
after all, no reason why it should not be possible for some heavenly body to
exist having this form, which, if not spherical, is at least round, and is
quite as well adapted to the possession of circumcentral motion as the
spherical form itself. For it certainly is less surprising that such a body
should have assigned to it a shape of this kind than that it should have some
absurd and quite unbeautiful shape. Furthermore, since, owing to the great
similarity and relationship that exists between Saturn and our Earth, it seems
possible to conclude quite conclusively that the former, like the latter, is
situated in the middle of its own vortex, and that its centre has a natural
tendency to reach toward all that is considered to have weight there, it must also
result that the ring in question, pressing with all its parts and with equal
force toward the centre, comes by this very fact to a permanent position in
such a way that it is equally distant on all sides from that centre. Exactly so
some people have imagined that, if it were possible to construct a continuous
arch all the way around the Earth, it would sustain itself without any support.
Therefore, let them not consider it absurd if a similar thing has happened of
itself in the case of Saturn; let them rather regard with awe the power and
majesty of Nature, which, by repeatedly bringing to light new specimens of its
works, admonishes us that yet more remain.
Christiaan
Huygens Systema Saturnium 1659
Christiaan Huygens
Next
to turn his telescope towards Saturn was our old friend Gian Domenico Cassini,
now overseeing the Paris observatory under the patronage of Louis XIV. Between
1671 and 1684 Cassini discovered four more moons of Saturn; Iapetus, Rhea,
Tethys and Dione. He named these moons the Sidera
Lodoicea or Louisean Stars in honour of his royal patron. He also
discovered in 1675 that Huygens had been incorrect in his assertion that the
ring was a single solid structure with his observation of a visible gap between
the rings which still goes by the name of the Cassini Division. Cassini correctly
deduced that the rings of Saturn were not a solid structure but rather were composed
of millions of tiny satellites orbiting the planet.
In 1789,
Hanoverian astronomer and composer William Herschel, a favourite of King George
III best known for his discovery of Uranus, began observations with his famous
Great Forty Foot Telescope. (Pictured above) On the very first night of using the giant instrument, Herschel
discovered another moon of Saturn; Mimas. Within a month he had discovered a
second; Enceladus. The forty footer was the largest telescope yet created. This
great ‘penetrator of the heavens’ as Herschel described it, was a national
sensation and challenged the Christian preconceptions of the day which still saw
the universe as a cosy firmament which enclosed God’s creation, in which Earth
remained of primary importance. Instead, Herschel, himself a firm believer in
the possibility of extra-terrestrial life, was revealing a boundless universe filled with
countless unknown and distant worlds. This new, bigger vision of the cosmos
made many uncomfortable and Herschel’s scientific endeavours were criticised by
more romantically inclined contemporaries such as Wordsworth and Blake who
dismissed the giant telescope as a sideshow. King George III however thought that
it was a marvellous device. ‘What what!’ And commissioned several smaller
instruments from Herschel for his own use. With such enthusiastic royal
support, a craze for studying the heavens was born in an Eighteenth Century
equivalent of the ‘Brian Cox effect’. Of which I am myself a recent victim.
Huygens’
Systema Saturnium
Herschel’s Great Forty Footer
http://www.branchcollective.org/?ps_articles=kathleen-lundeen-on-herschels-forty-foot-telescope-1789
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