Forming Jupiter, Saturn, Uranus and Neptune in few million years by core accretion

Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the Solar System’s giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks’ lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial Solar System orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30–100 m sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.Instituto de Astrofísica de La Plat

Forming Jupiter, Saturn, Uranus and Neptune in few million years by core accretion

Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the Solar System’s giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks’ lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial Solar System orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30–100 m sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.Instituto de Astrofísica de La Plat

Child Physical Abuse and Neglect

Although poor and inhumane treatment of children is not a new phenomenon (Doerner & Lab, 1998; Wolfe, 1999), child physical abuse and neglect were not identified as serious social problems until the 1960s, with the publication of Kempe and colleagues’ description of battered-child syndrome (Kempe, Silverman, Steele, Droegemueller, & Silver, 1962). In this influential study, Kempe and colleagues described the clinical manifestation of this syndrome in terms of the deleterious physical consequences maltreated children experienced, ranging from undetected outcomes to those that cause significant physical impairments. Rather than exploring the potential psychological sequelae of maltreated children, Kempe focused on detailing the psychiatric profiles of abusive parents. They concluded that, although not all maltreating parents possess severe psychiatric disturbances, “in most cases some defect in character structure is probably present; often parents may be repeating the type of child care practiced on them in their childhood” (p. 112). Since Kempe and colleagues’ original characterization of physical abuse, professionals have grappled with exactly how to define child maltreatment. As many have pointed out, child maltreatment is a complex and heterogeneous problem (e.g., Cicchetti, 1990; Wolfe & Mc- Gee, 1991; Zuravin, 1991) that is difficult to define (Wolfe, 1987, 1999). In a summary of definitional consider ations, Zuravin (1991) suggested that operational definitions of abuse and neglect should differentiate among subcategories of maltreating behavior and should consider issues such as severity and chronicity. Before we discuss the respective definitions of child physical abuse and neglect, we will briefly review the legal aspects of these definitions

Simultaneous formation of solar system giant planets

Context.In the last few years, the so-called Nice model has become increasingly significant for studying the formation and evolution of the solar system. According to this model, the initial orbital configuration of the giant planets was much more compact than the one we observe today. Aims.We study the formation of the giant planets in connection with several parameters that describe the protoplanetary disk.We aim to establish which conditions enable their simultaneous formation in line with the initial configuration proposed by the Nice model. We focus on the conditions that lead to the simultaneous formation of two massive cores, corresponding to Jupiter and Saturn, which are able to reach the cross-over mass (where the mass of the envelope of the giant planet equals the mass of the core, and gaseous runway starts), while two other cores that correspond to Uranus and Neptune have to be able to grow to their current masses. Methods.We compute the in situ planetary formation, employing the numerical code introduced in our previous work for different density profiles of the protoplanetary disk. Planetesimal migration is taken into account and planetesimals are considered to follow a size distribution between rmin p (free parameter) and rmax p = 100 km. The core;s growth is computed according to the oligarchic growth regime. Results. The simultaneous formation of the giant planets was successfully completed for several initial conditions of the disk. We find that for protoplanetary disks characterized by a power law (r.p), flat surface density profiles (p . 1.5) favor the simultaneous formation. However, for steep slopes (p . 2, as previously proposed by other authors) the simultaneous formation of the solar system giant planets is unlikely. Conclusions. The simultaneous formation of the giant planets . in the context of the Nice model . is favored by flat surface density profiles. The formation time-scale agrees with the estimates of disk lifetimes if a significant mass of the solids accreted by the planets is contained in planetesimals with radii <1 km.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Simultaneous formation of solar system giant planets

Context.In the last few years, the so-called Nice model has become increasingly significant for studying the formation and evolution of the solar system. According to this model, the initial orbital configuration of the giant planets was much more compact than the one we observe today. Aims.We study the formation of the giant planets in connection with several parameters that describe the protoplanetary disk.We aim to establish which conditions enable their simultaneous formation in line with the initial configuration proposed by the Nice model. We focus on the conditions that lead to the simultaneous formation of two massive cores, corresponding to Jupiter and Saturn, which are able to reach the cross-over mass (where the mass of the envelope of the giant planet equals the mass of the core, and gaseous runway starts), while two other cores that correspond to Uranus and Neptune have to be able to grow to their current masses. Methods.We compute the in situ planetary formation, employing the numerical code introduced in our previous work for different density profiles of the protoplanetary disk. Planetesimal migration is taken into account and planetesimals are considered to follow a size distribution between rmin p (free parameter) and rmax p = 100 km. The core;s growth is computed according to the oligarchic growth regime. Results. The simultaneous formation of the giant planets was successfully completed for several initial conditions of the disk. We find that for protoplanetary disks characterized by a power law (r.p), flat surface density profiles (p . 1.5) favor the simultaneous formation. However, for steep slopes (p . 2, as previously proposed by other authors) the simultaneous formation of the solar system giant planets is unlikely. Conclusions. The simultaneous formation of the giant planets . in the context of the Nice model . is favored by flat surface density profiles. The formation time-scale agrees with the estimates of disk lifetimes if a significant mass of the solids accreted by the planets is contained in planetesimals with radii <1 km.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Monitoring and analyzing exoplanetary transits from Argentina

Photometric observations of transits can be used to derive physical and orbital parameters of the system, like the planetary and stellar radius, orbital inclination and mean density of the star. Furthermore, monitoring possible periodic variations in transit timing of planets is important, since small changes can be caused by the presence of other planets or moons in the system. On the other hand, long term changes in the transit length can be due to the orbital precession of the planets. For these reasons we started an observational program dedicated to observe transits of known exoplanets with the aim of contributing to a better understanding of these planetary systems. In this work we present our first results obtained using the observational facilities in Argentina including the 2.15 telescope at CASLE

Monitoring and analyzing exoplanetary transits from Argentina

Photometric observations of transits can be used to derive physical and orbital parameters of the system, like the planetary and stellar radius, orbital inclination and mean density of the star. Furthermore, monitoring possible periodic variations in transit timing of planets is important, since small changes can be caused by the presence of other planets or moons in the system. On the other hand, long term changes in the transit length can be due to the orbital precession of the planets. For these reasons we started an observational program dedicated to observe transits of known exoplanets with the aim of contributing to a better understanding of these planetary systems. In this work we present our first results obtained using the observational facilities in Argentina including the 2.15 telescope at CASLEO.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Forming Jupiter, Saturn, Uranus and Neptune in Few Million Years by Core Accretion

Giant planet formation process is still not completely understood. The current most accepted paradigm, the core instability model, explains several observed properties of the solar system's giant planets but, to date, has faced difficulties to account for a formation time shorter than the observational estimates of protoplanetary disks' lifetimes, especially for the cases of Uranus and Neptune. In the context of this model, and considering a recently proposed primordial solar system orbital structure, we performed numerical calculations of giant planet formation. Our results show that if accreted planetesimals follow a size distribution in which most of the mass lies in 30-100 meter sized bodies, Jupiter, Saturn, Uranus and Neptune may have formed according to the nucleated instability scenario. The formation of each planet occurs within the time constraints and they end up with core masses in good agreement with present estimations.Comment: 11 pages, 3 figures, in press (Icarus