Photometric survey of the irregular satellites

Abstract

We present BVRI colors of 13 Jovian and 8 Saturnian irregular satellites obtained with the 2.56m Nordic Optical Telescope on La Palma, the 6.5m Magellan Baade Telescope on La Campanas, and the 6m MMT on Mt. Hopkins. The observations were performed between December 2001 to March 2002. Nearly all of the known irregular satellites can be divided into two distinct classes based on their colors. One, the grey color class, has the similar colors to the C-type asteroid, and the other, the light red color class, has colors similar to P/D-type asteroids. We also find at least one object, the Jovian irregular J XXIII Kalyke, that has colors similar to the red colored Centaurs/TNOs, although its classification is unsecure.We find that there is a correlation between the physical properties and dynamical To which of these two clusters the remaining Saturnian irregulars with inclinations close to 174• belong is not clear from our analysis, but determination of their colors should help constrain this.We also show through analysis of possible fragmentation and dispersion of the six known Uranian irregulars that they most likely make up two clusters, one centered on U XVI Caliban and another centered on U XVII Sycorax. We further show that, although -4 -the two objects have similar colors, a catastrophic fragmentation event creating one cluster containing both U XVI Caliban and U XVII Sycorax would have involved a progenitor with a diameter of ∼ 395km. While such an event is not impossible it seems rather improbable, and further we show that such an event would leave 5-6 fragments with sizes comparable or lager than U XVI Caliban. Given that the stable region around Uranus has been extensively searched to limiting magnitudes far beyond that of U XVI Caliban. The fact that only U XVI Caliban and the larger U XVII Sycorax have been found leaves us with a distribution not compatible with a catastrophic event with such a large progenitor. The most likely solution is therefore two separate events creating two Uranian dynamical clusters.

Capture of Irregular Satellites during Planetary Encounters

“…Spectroscopic studies show a large diversity of colors (ranging from gray to very red ) among observed irregular satellites of four outer planets (Cruikshank 1980;Degewij et al 1980;Dumas et al 1998;Brown 2000;Sykes et al 2000;Grav et al 2003Porco et al 2005). This diversity would be difficult to understand if irregular satellites were captured from a local and dynamically cold population of planetesimals at the planet's heliocentric position, because in such a case the colors should be homogeneous (reflecting the local composition) and there should exist a clear color gradient of irregular satellites with heliocentric distance (i.e., from Jupiter to Neptune).…”

Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos, and Trinculo

“…All of this seems to support the idea of a collisional scenario. However, the existence of a dynamical grouping (Kavelaars et al 2004;Sheppard et al 2005) is still debated on the light of the colour determination of Grav et al (2004b). Regrettably, there seems to be a lack of consistency between B − V and V − R colours of different authors for Sycorax and Caliban (Maris et al 2001;Rettig et al 2001;Romon et al 2001;Grav et al 2004a).…”

Addition of nanoparticle dispersions to enhance flux pinning of the YBa2Cu3O7-x superconductor

“…Photometry of the jovian and saturnian irregular satellites shows that most satellite clusters have homogeneous colours, thus intimating that irregulars are collisional fragments of larger progenitors 28,29 . Following the discovery of type-II high-temperature superconductors in 1986 (refs 1, 2), work has proceeded to develop these materials for power applications.…”