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The Lagrange planetary equations are used to study to secular evolution of a small, eccentric satellite that orbits within a narrow gap in a broad, self-gravitating planetary ring. These equations show that the satellites secular perturbations of the ring will excite a very long-wavelength spiral density wave that propagates away from the gaps outer edge. The amplitude of these waves, as well as their dispersion relation, are derived here. That dispersion relation reveals that a planetary ring can sustain two types of density waves: long waves that, in Saturns A ring, would have wavelengths of order 100 km, and short waves that tend to be very nonlinear and are expected to quickly damp. The excitation of these waves also transports angular momentum from the ring to the satellite in a way that damps the satellites eccentricity e, which also tends to reduce the amplitude of subsequent waves. The rate of eccentricity damping due to this wave action is then compared to the rates at which the satellites Lindblad and corotation resonances alter the satellites e. These results are then applied to the gap-embedded Saturnian satellites Pan and Daphnis, and the long-term stability of their eccentricities is assessed.
The secular perturbations exerted by an inclined satellite orbiting in a gap in a broad planetary ring tends to excite the inclinations of the nearby ring particles, and the rings self-gravity can allow that disturbance to propagate away in the form
We present our recent results on the properties of the outskirts of disk galaxies. In particular, we focus on spiral galaxies with stellar disk truncations in their radial surface brightness profiles. Using SDSS, UDF and GOODS data we show how the po
Aside from the grand-design stellar spirals appearing in the disk of M81, a pair of stellar spiral arms situated well inside the bright bulge of M81 has been recently discovered by Kendall et al. (2008). The seemingly unrelated pairs of spirals pose
We present an analysis of the impact of spiral density waves (DWs) on the radial and surface density distributions of supernovae (SNe) in host galaxies with different arm classes. We use a well-defined sample of 269 relatively nearby, low-inclination
The Neptunian satellite system is unusual. The major satellites of Jupiter, Saturn, and Uranus are all in prograde, low-inclination orbits. Neptune on the other hand, has the fewest satellites, and most of the systems mass is within one irregular sat