Quite often in astronomy objects which appear at first glance to be ordinary and uninteresting are very much the opposite in reality. Such is the case in this month’s Colorado sky for the seemingly unremarkable golden planet Saturn.
Currently located to the north of the bright reddish Scorpius star Antares, Saturn possesses a respectable brightness compared to the stars of the summertime zodiac, but compared to the other naked-eye planets, Saturn is not a standout object by any means. For example, the planet Mars, one constellation to the west in Libra, is currently five times brighter than Saturn. A view through even a small telescope, however, transforms this respectably bright naked eye object into one of the most beautiful sights in all of the heavens.
The source of this legendary beauty is, of course, the famed ring system of Saturn which girds the planet at its equator and extends over a diameter of some 200,000 miles. Saturn and its ring system are so unique in nature that cartoons, comic strips, movies and other media routinely employ the Ringed Planet as a vehicle to denote outer space and other world settings, thus elevating Saturn and its rings to the premier outer space logo.
Early on, Saturn’s ring system enveloped the planet with an air of mystery for 17th Century Renaissance astronomers whose primitive telescopes were not yet powerful enough to detect its true nature. Thus, famed astronomers such as Galileo, reported that Saturn seemed to have ‘ears,’ ‘knobs,’ or some other type of “appendages” attached to the planet’s main disk. In 1659, using more powerful telescopes, the Dutch astronomer Christiaan Huygens was able to ascertain the true nature of the Saturnian “appendages.”
For more than three centuries afterward, astronomers carefully crafted a portrait of the rings and how they might have formed. The prevailing view was that a small ice satellite of Saturn drifted too close to the planet and was tidally torn apart by Saturn’s differential gravitation. The debris from this tidal disruption fanned out into the extensive but extremely thin ring-shaped plane of debris that we see today. Small-scale gravitational effects from Saturn’s major satellites then sculpted a pattern of gaps and divisions in the debris, the most noteworthy of which is the prominent gap known as Cassini’s division. Scientists became smugly confident that all of the observed properties of Saturn’s ring system could be explained within the context of this overall scenario.
So often it happens in science that just when we think we have completely figured out some aspect of the physical world, fundamental surprises almost certainly wait just around the corner. Such was the case with Saturn’s ring system. The Pioneer and Voyager space probes of the 1970s and 1980s discovered that Saturn’s rings are far more complex than anyone imagined. Images from these space probes revealed that Saturn’s rings consist of several hundred rope-like structures, each of which is about a mile in diameter, tens of thousands of miles long, and is composed of a myriad of basketball-sized ice particles. Amazingly these “ringlets,” as they are called, exhibit a wide variety of mysterious characteristics. Some of the ringlets intertwine or “braid” with one another, while others exhibit variable thicknesses. A few of the ringlets only partially circle Saturn, suddenly stopping as if being snipped off at the ends, and spoke-like features appear and vanish as they move outward from the innermost ringlets.
Observations of Saturn’s ring system made by the Cassini space probe orbiting Saturn since 2004 have added even more puzzling contributions to the list of amazingly wonderful phenomena that have been observed in the Saturnian ring system, thereby lending yet another dimension to a continuously unfolding mystery which began 400 years ago when human beings took their first telescopic views of this golden ringed wonder of the heavens.
Elsewhere in the sky: The planet Jupiter glows as a yellowish-white object to the south of the constellation of Leo and can be seen above the western horizon for about three hours or so after sunset.
As mentioned above, the planet Mars is now shining brightly to the west of Saturn in eastern Libra.
The planets Mercury and Venus are too close to the sun to be easily seen in July.