Star date: 10:04:98
There are occasional gatherings around
the country of people seeking to look through a telescope, many
of them for the first time. These "star parties", as
they are known, have increased in popularity over the course of
the last few decades.
The inexpensive surplus army optics available after World War II led many people with an interest in astronomy into buiding their own telescopes. Many of these people took their telescopes to public places and allowed, and even encouraged the general public to look through their telescopes at a variety of astronomical objects.
One of the people who led some of these early star parties was an ex-monk from San Francisco named John Dobson. In a quest not only to educate the public, but also to make astronomy accessible to as many people as possible, Dobson invented a simple mount to use on his telescopes, which became known as the Dobsonian mount. The popularity of these mounts is astounding, and is now the fastest growing segment of the telescope mount market.
The people who lead these star parties often choose which objects will be being viewed that night. At every star party, however, there are requests from the participents as to what to look for. What is far and away the most requested object in the night sky? It is, at least in my experience, the planet Saturn. Why Saturn? The planet itself is a bland, yellow/tan color, and the only really interesting feature is a couple of white bands which have recently appeared, encircling the planet. No, Jupiter is far prettier, white multi-hued tans, browns, whites, and orange bands.
There is at least one moon of Saturn which is easily visible with any backyard telescope. This is the giant moon Titan, larger than either the planets Mercury or Pluto. Again, Jupiter has more to offer in this department as well, with four moons which can be seen in a small astronomical instrument. These are the so called "Galilean Moons" of Jupiter, Io, Europa, Ganymede, and Callisto. Galileo saw them with a primitive one inch refracting telescope in the year 1610.
There are polar ice caps on Mars, Venus and Mercury display phases as seen from Earth, and viewing Uranus or Neptune allows you the thrill of seeing something which is not visible to the naked eye. So why is Saturn the most sought after astronomical object among much of the general population? The answer is simple: Saturn's magnificent set of rings. The planets Jupiter, Uranus, and Neptune also have rings, but they are so dim and thin that the first of them (Jupiter's) was not discovered until 1979. The rings of Saturn are 1000 times brighter than the rings of Jupiter. Saturns rings, were another discovery by Galileo (in the year 1609), but he at first believed the rings to be two seperate objects, one on each side of the planet, and described them as "ears".
Exactly 50 yeasr later,
the astronomer Christian Huygens realized that the rings were
not attached to the planet, but were, instead, a disk orbiting
around, but never touching the planet. We now know that the rings
of Saturn are actually composed of thousands of tiny ringlets,
locked in a graviatational dance with one another as they circle
the planet. Of these thousands of ringlets, there are two, and
perhaps three groups of rings are visible from the Earth using
backyard telescopes and binocluars.
When you look at Saturn, you should be able to see a gap in the rings. This is called the Cassini division, after its discoverer. The group of rings on the outside of this gap is called the A ring. The group on the inside of the Cassini division is known (not surprisingly) as the B ring. A challenge as you are observing Saturn is to see if you can spot the thin, ghost like C ring. It can be seen just inside of the B ring, with the darkness of space barely visible behind its thin sheen. The B ring is the widest across of these, streching over 25,000 km (15,625 miles) across. On the other side of the Cassini division, which is itself 3500 km (nearly 2200 miles) across, lies the B ring, which is the widest across of these sets of rings. The B ring is an astonishing 25,500 kilmeters across. This is equal to nearly 16,000 miles. This is the same as two Earths lied side to side.
Two hundred years after
Huygen's research, in the year 1859, James Maxwell, who became
famous for his work with electricity, proved that Saturn's rings
could not be solid objects. According to Kepler's third law, the
parts of the rings on the outside orbit at a slower velocity than
parts further in. This would quickly rip the rings apart. The
Voyager encounters with Saturn in the early 1980's showed, for
the first time, pictures of the multitudes of rings in their celestial
embrace. The fine detail in the structure of Saturns rings looks
like a phonograph record with a light shining on it.
Saturn experiences seasons as the Earth does, and this causes the rings to appear at various angles from year to year as seen from Earth. The rings are now tilted at nearly 20 degrees, ideal for observation. Look for Saturn less than 10 degrees north of east at 10pm, and just a few degrees above the horizon. Later in the evening, it will be higher in the sky, and moving further towards first the east, then continuing towards the south later in the night.
Clear skies, and good viewing.
