On the origin of comet C/1999 S4 LINEAR

Abstract

Abstract. Current models of the formation of comets in the Solar System assume that the most likely formation site for these pristine objects is in the Uranus-Neptune zone or just beyond with subsequent dynamical ejection by the growing protoplanets to distant orbits to form the Oort cloud. However, the composition of the recently disintegrated comet C/1999 S4 LINEAR suggests that it was most likely formed in the Jupiter-Saturn region (Mumma et al. 2001b;Kawakita et al. 2001). In this paper we argue that cometesimals could easily appear inside exterior resonances resulting from gas drag, between the orbits of Jupiter and Saturn and beyond Saturn, during the formation of these giant planets. Then, the trapped material could evolve into actual comets by means of collisional coagulation, followed by gravitational instability of a layer of macroscopic bodies or two-body accretion. Properties of these objects would be rather different from those found in classical comets formed beyond Neptune as a result of different physicochemical environment. Our results also suggest that temporarily stable cometary belts may have existed in the Jupiter-Saturn region. We also discuss the implications of this scenario on the existence of a bimodal Centaur population.

Clusters and mirages: cataloguing stellar aggregates in the Milky Way

“…Cantat- Gaudin et al (2018a) were unable to identify any such co-moving group in the Gaia DR2 catalogue, and Kos et al (2018) also failed to identify one despite complementing the Gaia DR2 data with new high-resolution spectroscopy. They also point out that not a single pair of stars in the entire member lists of Bouchet & The (1983), Pavani et al (2001), de la Fuente Marcos et al (2013), and Kharchenko et al (2013) have matching astrometric parameters. NGC 1252 is listed as an asterism in Bica et al (2019) and Angelo et al (2019b).…”

“…The object is included in the DAML and MWSC catalogues (with quoted distances of 790 and 944 pc, respectively) and is also present in the study of Pavani & Bica (2007). de la Fuente Marcos et al (2013) collected additional data and reported that most stars in the investigated region are 'chemically, kinematically, and spatially unrelated to each other' but still argue that a handful of faint stars might be co-moving, making this 'enigmatic object' the first old, high-altitude (b = −50.8 • ), nearby open cluster. Kharchenko et al (2013) also provide the result of an isochrone fitting procedure for NGC 1252, indicating an old age of log t=9.5…”

Synthesis of Gold(I) Derivatives Bearing Alkylated 1,3,5‐Triaza‐7‐phosphaadamantane as Selective Anticancer Metallodrugs

“…For instance, the functionalization of peptides with gold nanoparticles to afford biocompatible nanoparticles able to penetrate the cell membrane and target the nucleus has been described recently. [31][32][33] In addition, a number of gold conjugates derived from amino acids or peptides have been reported. As examples, N-heterocyclic carbene (NHC)-gold complexes, [34,35] conjugates of ferrocene coordinated to gold(I) derivatives, [36] gold(III) dithiocarbamates, [37,38] gold(I) azides, [39] and gold(I) thi-of the phosphorus atom to the gold(I) centre, as evidenced by the downfield displacement of the singlets in the 31 P{ 1 H} NMR spectra.…”

Searching for the lost Unicorn: a prominent feature in the radial velocity distribution of stars in Vela from Gaia DR2 data

“…It may be argued that both peaks in the distribution of radial velocity in Fig. 1, bottom panel, could be the result of the presence of small, distant, and decaying clusters such as E 3 (de la Fuente Marcos et al 2015). In such cases, we should observe very small concentrations of relevant sources.…”