Ringmoons And Ringlets

As discussed in Chapter 9 and Section 10.3, moonlets are intimately intermingled in all planetary ring-moon systems. Those orbiting within and just outside Saturn's main rings are responsible for exciting a large number of spiral density waves, such as those in Figures 10.6 and 10.7, which may be used to determine their mass. Since we now have very good images of these moons giving their volume, we can easily determine their density. All the close-in ringmoons of Saturn have a density about...

Nomenclature And Radial Dimensions Of The Saturnian Rings

In Chapter 2, the discovery of Saturn's rings was discussed in detail. A general qualitative description of the rings was included with that discussion, as was the nomenclature of the individual ring regions. In Table 9.1, adapted from Cuzzi et al. 1 , the orbital characteristics and estimated masses of the rings are given. For comparison, we also include the inner eight satellites of Saturn known prior to Cassini. The narrow F ring was first discovered by Pioneer 11 during its encounter with...

The Nature Of The Rings

The ring's thickness was not the only erroneous conclusion Huygens had made about the ring Huygens had also proposed that the ring was a solid body 12 . First, astronomers had difficulties explaining the stability and periodic motions of a solid spinning ring. Remember that astronomers of the day did not yet understand the law of gravitation or the laws of planetary motions. Newton's Principia Mathematica, which contained the first formulation of the law of gravitation, would not be published...

Summary And Major Unanswered Questions Before Cassini

The purpose of this chapter has been to set the stage for the spectacular data on Saturn's rings returned by the Cassini Orbiter. In Chapter 10 we report on some of the preliminary findings of this important international space mission. Hopefully, the data we include in this book will whet the appetites of interested readers sufficiently to cause them to search for the later results that will already have appeared or will shortly appear that further expand on our understanding of the Saturn...

First Observations Of Saturns Companions

The invention of the telescope ended the age of naked-eye astronomy. Astronomers no longer needed to scan the heavens with their eyes alone. The looking glass opened the solar system and indeed the universe to the scrutiny of humanity. The first recorded use of the telescope for astronomical study was performed in 1610 by Galileo Galilei. Using just a 20-powered spyglass, Galileo discovered spots on the Sun, four satellites about Jupiter, and surface features on the Moon see Figure 2.1 . His...

Ring Dimensions

With the exception of the only known blue-tinted rings Saturn's E ring and Uranus's recently discovered 2003U1R ring, both of which appear to be composed of water-ice particles derived from satellites Enceladus and Mab, respectively , all of the known planetary rings are found within 3.2 planetary radii of the centers of their respective planets Figure 11.1 . Well exterior to these rings whose radial positions and dimensions are catalogued in Table 11.1, Uranus and Neptune have dust disks...

List of abbreviations and acronyms

Galileo Millennium Mission Extension InfraRed Interferometer Spectrometer and radiometer International Space Station Imaging Science Subsystem NASA's Gerard P. Kuiper Airborne Observatory Maneuverless Image Motion Compensation National Aeronautics and Space Agency National Radio Astronomy Observatory Visible and Infrared Mapping Spectrometer

Notes And References

1 Table 9.1 is adapted from table 1 in Cuzzi, J. N., Colwell, J. E., Esposito, L. W., Porco, C. C., Murray, C. D., Nicholson, P. D., Spilker, L. J., Marouf, E. A., French, R. C., Rappaport, N., Muhleman, D., 2003, Saturn's rings Pre-Cassini status and mission goals, Space Science Reviews 118, 209-251. 2 Cuzzi, J. N., Pollack, J. B., 1978, Saturn's rings Particle composition and size distribution as constrained by microwave observations'', Icarus 33, 233-262. 3 Figure 9.4 is from Estrada, P....

Major Differences Between The Known Ring Systems

While the similarities between the ring systems are primarily those that provide a description of planetary ring systems in general, it is the differences that give each ring system its own unique personality and appearance. It is also these individually unique personalities that provide the motivation for this book. Without that diversity, a treatise on planetary ring systems might require little more than a 15-page illustrated magazine article. In this introductory chapter, only a few of the...

Earthbased Observations Of Saturns Rings Since

There are three primary types of observations of Saturn's rings that have provided additional information on the ring system since the Voyager encounters in 1980 and 1981. These include an occultation of the star 28 Sagittarii by Saturn and its rings in 1989, observations at the time of the ring plane crossings of the Earth and the Sun in 1995 and 1996, and radar observations of the rings from the Arecibo Observatory in Puerto Rico from 1999 onward. In addition, there was an extended series of...

Model For The Ring Emerges

In 1642 astronomers began once again to take interest in the problem of Saturn's companions and their slowly changing shape. Notable astronomers like Pierre Gassendi 1592-1655 , Francesco Fontana 1585-1656 , Antonius Maria Schyrlaeus de Rheita 1597-1660 and Johannes Hevelius 1611-1687 all began to make systematic observations of the planet 8 . Although the accumulation of a greater number of observations was necessary for determining the true nature of Saturn and its companions, many of the...

Smaismrmilmepoetaleumibunenugttauiras

Italian astronomer Galileo announced with this anagram sent to his patron astronomer Johannes Kepler on July 30, 1610, that unscrambling his anagram , ALTIS-SIMUM PLANETAM TERGEMINUM OBSERVAVI. Roughly interpreted out of the Latin, Galileo was telling his colleague, I have observed that the most distant of planets has a triple form. Note that U and V are interchangeable in Latin. Of course, Kepler did not understand what Galileo was announcing until Galileo himself later unscrambled the...

Ring Dimensions Shapes And Inclinations

Table 7.1 provides an overview of the mean radial distances, velocities, periods, and masses of the 13 known rings and the 14 inner satellites of Uranus 1 . Their widths, orbital eccentricities and inclinations, and equivalent depths are given in Table 7.2 2 . Because the eccentric rings have widths that vary with orbital longitude, the concept of equivalent depth physical width multiplied by optical depth is important because it remains essentially constant around the ring and is a measure of...

Gossamer Rings

The inner Gossamer ring has as its source the satellite Amalthea see Figure 6.1 . Amalthea has a mean diameter of 167 km, but more importantly it has an orbital inclination to Jupiter's equator of 0.388 . With its mean orbital radius of 181,400km, an inclination of 0.388 leads to excursions above and below Jupiter's equator of 1,230 km, or a full thickness of 2,460 km. If one then adds Amalthea's mean diameter of 172 km, the result is remarkably close to the 2,600-km estimated thickness of the...