In the coming years, high-contrast imaging surveys are expected to reveal the characteristics of the population of wide-orbit, massive, exoplanets. To date, a handful of wide planetary mass companions are known, but only one such multi-planet system has been discovered: HR 8799. For low mass planetary systems, multi-planet interactions play an important role in setting system architecture. In this paper, we explore the stability of these high mass, multi-planet systems. While empirical relationships exist that predict how system stability scales with planet spacing at low masses, we show that extrapolating to super-Jupiter masses can lead to up to an order of magnitude overestimate of stability for massive, tightly packed systems. We show that at both low and high planet masses, overlapping mean-motion resonances trigger chaotic orbital evolution, which leads to system instability. We attribute some of the difference in behavior as a function of mass to the increasing importance of second order resonances at high planet-star mass ratios. We use our tailored high mass planet results to estimate the maximum number of planets that might reside in double component debris disk systems, whose gaps may indicate the presence of massive bodies.

We present the. Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 mu m, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 mu m. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well matched by a clear H-2-dominated atmosphere, or one containing a weak contribution from haze, in good agreement with the preliminary reduction of these data presented in Sing et al.. WASP-39b is predicted to have a pressure-temperature profile comparable to that of HD 189733b and WASP-6b, making it one of the coolest transiting gas giants observed in our HST STIS survey. Despite this similarity, WASP-39b appears to be largely cloud-free, while the transmission spectra of HD 189733b and WASP-6b both indicate the presence of high altitude clouds or hazes. These observations further emphasize the surprising diversity of cloudy and cloud-free gas giant planets in short-period orbits and the corresponding challenges associated with developing predictive cloud models for these atmospheres.

We present new H (1.51.8 mu m) photometric and K-1 (1.92.2 mu m) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The Hband magnitude has been significantly improved relative to previous measurements, whereas the lowresolution K-1 (lambda/delta lambda approximate to 66) spectrum is featureless within the measurement uncertainties and presents a monotonically increasing pseudocontinuum consistent with a cloudy atmosphere. By combining these new measurements with literature L' photometry, we compare the spectral energy distribution (SED) of the planet to other young planetarymass companions, field brown dwarfs, and to the predictions of grids of model atmospheres. HD 95086 b is over a magnitude redder in K-1 - L' color than 2MASS J120733463932539 b and HR 8799 c and d, despite having a similar L' magnitude. Considering only the near-infrared measurements, HD 95086 b is most analogous to the brown dwarfs 2MASS J2244316+204343 and 2MASS J21481633+4003594, both of which are thought to have dusty atmospheres. Morphologically, the SED of HD 95086 b is best fit by low temperature (T-eff = 8001300 K), low surface gravity spectra from models which simulate high photospheric dust content. This range of effective temperatures is consistent with field L/T transition objects, but the spectral type of HD 95086 b is poorly constrained between early L and late T due to its unusual position the colormagnitude diagram, demonstrating the difficulty in spectral typing young, low surface gravity substellar objects. As one of the reddest such objects, HD 95086 b represents an important empirical benchmark against which our current understanding of the atmospheric properties of young extrasolar planets can be tested.

Low mass, self-gravitating accretion disks admit quasi-steady, "gravito-turbulent" states in which cooling balances turbulent viscous heating. However, numerical simulations show that gravito-turbulence cannot be sustained beyond dynamical timescales when the cooling rate or corresponding turbulent viscosity is too large. The result is disk fragmentation. We motivate and quantify an interpretation of disk fragmentation as the inability to maintain gravito-turbulence due to formal secondary instabilities driven by: (1) cooling, which reduces pressure support; and/or (2) viscosity, which reduces rotational support. We analyze the axisymmetric gravitational stability of viscous, non-adiabatic accretion disks with internal heating, external irradiation, and cooling in the shearing box approximation. We consider parameterized cooling functions in 2D and 3D disks, as well as radiative diffusion in 3D. We show that generally there is no critical cooling rate/viscosity below which the disk is formally stable, although interesting limits appear for unstable modes with lengthscales on the order of the disk thickness. We apply this new linear theory to protoplanetary disks subject to gravito-turbulence modeled as an effective viscosity, and cooling regulated by dust opacity. We find that viscosity renders the disk beyond similar to 60 au dynamically unstable on radial lengthscales a few times the local disk thickness. This is coincident with the empirical condition for disk fragmentation based on a maximum sustainable stress. We suggest turbulent stresses can play an active role in realistic disk fragmentation by removing rotational stabilization against self-gravity, and that the observed transition in behavior from gravito-turbulent to fragmenting may reflect instability of the gravito-turbulent state itself.

This overview paper describes the legacy prospect and discovery potential of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it with examples from the DES early data. DES is using a wide-field camera (DECam) on the 4 m Blanco Telescope in Chile to image 5000 sq deg of the sky in five filters (grizY). By its completion, the survey is expected to have generated a catalogue of 300 million galaxies with photometric redshifts and 100 million stars. In addition, a time-domain survey search over 27 sq deg is expected to yield a sample of thousands of Type Ia supernovae and other transients. The main goals of DES are to characterize dark energy and dark matter, and to test alternative models of gravity; these goals will be pursued by studying large-scale structure, cluster counts, weak gravitational lensing and Type Ia supernovae. However, DES also provides a rich data set which allows us to study many other aspects of astrophysics. In this paper, we focus on additional science with DES, emphasizing areas where the survey makes a difference with respect to other current surveys. The paper illustrates, using early data (from 'Science Verification', and from the first, second and third seasons of observations), what DES can tell us about the Solar system, the Milky Way, galaxy evolution, quasars and other topics. In addition, we show that if the cosmological model is assumed to be I >+cold dark matter, then important astrophysics can be deduced from the primary DES probes. Highlights from DES early data include the discovery of 34 trans-Neptunian objects, 17 dwarf satellites of the Milky Way, one published z > 6 quasar (and more confirmed) and two published superluminous supernovae (and more confirmed).

The search for planets orbiting stars other than the Sun has led to the discovery of over one thousand new worlds. The majority of these planets have been very large, Jupiter sized planets located very close to their host star. Transit surveys such as Kepler and SuperWASP monitor thousands of stars looking for periodic dips in light caused by a planet passing between our view point on Earth and their host star, blocking a fraction of the emitted star light. One of the primary limitations in detecting a small, Earth sized planet comes from stellar activity induced signals within the data collected by exoplanet missions. These signals can, however, be used to our advantage. In this thesis, asymmetries in transit light curves are exploited to reveal properties of both the planet and the host stars themselves. An asymmetry in the near-ultraviolet transit light curve of WASP-12b, one of the largest and hottest planets found to date is thought to be caused by the stellar wind interacting with the magnetic field surrounding the planet. In this thesis, a model for such an interaction is developed and is shown to be consistent with the observations, providing the first potential evidence for the presence of a magnetic field around an exoplanet. The model is then extended to predict the shape of near-ultraviolet light curves around HD 189733b, another hot Jupiter that orbits a very bright star. By looking at the variability in these transit light curves over time, the evolution and structure of the stellar wind is investigated. By tracking the position of bumps in the transit light curve, it is shown here that the data collected by missions such as Kepler has the potential to reveal stellar butterfly patterns. Such patterns are intrinsically linked with the stellar dynamo which governs the properties of the stellar magnetic field. Finally, the support of large-scale magnetic loops on young stars is investigated. These loops trap large amounts of hot, dense material and so a rapid destabilisation could lead to a flaring event, which could have devastating consequences for a nearby exoplanet.

The Pluto-Charon system has come into sharper focus following the flyby of New Horizons. We use N-body simulations to probe the unique dynamical history of this binary dwarf planet system. We follow the evolution of the debris disc that might have formed during the Charon-forming giant impact. First, we note that in situ formation of the four circumbinary moons is extremely difficult if Charon undergoes eccentric tidal evolution. We track collisions of disc debris with Charon, estimating that hundreds to hundreds of thousands of visible craters might arise from 0.3-5 km radius bodies. New Horizons data suggesting a dearth of these small craters may place constraints on the disc properties. While tidal heating will erase some of the cratering history, both tidal and radiogenic heating may also make it possible to differentiate disc debris craters from Kuiper belt object craters. We also track the debris ejected from the Pluto-Charon system into the Solar system; while most of this debris is ultimately lost from the Solar system, a few tens of 10-30 km radius bodies could survive as a Pluto-Charon collisional family. Most are plutinos in the 3: 2 resonance with Neptune, while a small number populate nearby resonances. We show that migration of the giant planets early in the Solar system's history would not destroy this collisional family. Finally, we suggest that identification of such a family would likely need to be based on composition as they show minimal clustering in relevant orbital parameters.

Este trabalho tem por objetivo analisar as concepções a respeito de átomos e elementos químicos, expressas pelo químico russo Dmitri I. Mendeleev (1834 - 1907). Para isso, recorremos a textos desse autor que foram traduzidos para o inglês, principalmente seu livro didático Principles of Chemistry, mas também os artigos \"An Attempt to Apply to Chemistry one of The Principles of Newton\"s Natural Philosophy\", (1889) e \"An Attempt towards a chemical conception of the ether\", (1902). No decorrer do século XIX, a hipótese atômica formulada por Dalton, e elaborada por outros químicos, ainda não era unanimemente aceita pela comunidade científica. Nesse contexto, observamos que Mendeleev se alinhava aos autores que tinham reservas quanto à realidade física dos átomos. Para compreender seus motivos, é importante considerar que os primeiros estudos científicos de Mendeleev se referiam aos chamados \"compostos indefinidos\", isto é, compostos que não obedeciam à lei das proporções múltiplas de Dalton. Mendeleev reconhecia que a hipótese atômica explicava uma série de fenômenos químicos, mas não era capaz de explicar os compostos indefinidos. Por outro lado, Mendeleev propôs uma clara distinção entre os conceitos de elemento químico e de corpo simples. Os elementos seriam entidades abstratas, portadoras da individualidade química, ideia considerada fundamental por Mendeleev e que o conduziu à formulação da lei periódica. Nos escritos analisados, Mendeleev fez uso, de maneira recorrente, da analogia entre o sistema solar e as moléculas. Nessa analogia, os planetas remetem à ideia de individualidade, essencial para a compreensão do conceito de elemento químico; mas, ao mesmo tempo, não remetem à ideia de indivisibilidade física - o ponto da hipótese atômica que por muito tempo foi objeto de descrença por parte de Mendeleev. / This work aims to analyze the concepts of atom and chemical elements, as presented in the writings of the Russian chemist Dmitri I. Mendeleev, (1834 - 1907). In this analysis were used English translations of Mendeleev\"s texts, especially his textbook Principles of Chemistry, but also the papers \"An Attempt to Apply to Chemistry one of The Principles of Newton\'s Natural Philosophy\", (1889) and \"An Attempt Towards a chemical conception of the ether\", (1902). During the nineteenth century, the atomic hypothesis, proposed by Dalton and elaborated by other chemists, was not unanimously accepted by the scientific community. In this context, one may note that Mendeleev was aligned with authors who had reservations about the physical reality of atoms. To understand his reasons, it is important to consider that the first scientific researches performed by Mendeleev were on the so-called indefinite compounds, that is, compounds that did not obey Dalton\"s law of multiple proportions. Mendeleev recognized that the atomic hypothesis explained a series of chemical phenomena, but it could not explain indefinite compounds. Moreover, Mendeleev proposed a clear distinction between the concepts of chemical elements and simple bodies. Elements were abstract entities with chemical individuality, a crucial idea to Mendeleev that led him to the proposition of the periodic law. In the analyzed texts, Mendeleev used, on a recurring basis, the analogy between the solar system and molecules. In this analogy, planets relate to the idea of individuality, which is essential to understand the concept of chemical element, but at the same time does not refer to the idea of physical indivisibility - the point of the atomic hypothesis that has long been subject to disbelief by Mendeleev.

Este trabalho tem por objetivo analisar as concepções a respeito de átomos e elementos químicos, expressas pelo químico russo Dmitri I. Mendeleev (1834 - 1907). Para isso, recorremos a textos desse autor que foram traduzidos para o inglês, principalmente seu livro didático Principles of Chemistry, mas também os artigos \"An Attempt to Apply to Chemistry one of The Principles of Newton\"s Natural Philosophy\", (1889) e \"An Attempt towards a chemical conception of the ether\", (1902). No decorrer do século XIX, a hipótese atômica formulada por Dalton, e elaborada por outros químicos, ainda não era unanimemente aceita pela comunidade científica. Nesse contexto, observamos que Mendeleev se alinhava aos autores que tinham reservas quanto à realidade física dos átomos. Para compreender seus motivos, é importante considerar que os primeiros estudos científicos de Mendeleev se referiam aos chamados \"compostos indefinidos\", isto é, compostos que não obedeciam à lei das proporções múltiplas de Dalton. Mendeleev reconhecia que a hipótese atômica explicava uma série de fenômenos químicos, mas não era capaz de explicar os compostos indefinidos. Por outro lado, Mendeleev propôs uma clara distinção entre os conceitos de elemento químico e de corpo simples. Os elementos seriam entidades abstratas, portadoras da individualidade química, ideia considerada fundamental por Mendeleev e que o conduziu à formulação da lei periódica. Nos escritos analisados, Mendeleev fez uso, de maneira recorrente, da analogia entre o sistema solar e as moléculas. Nessa analogia, os planetas remetem à ideia de individualidade, essencial para a compreensão do conceito de elemento químico; mas, ao mesmo tempo, não remetem à ideia de indivisibilidade física - o ponto da hipótese atômica que por muito tempo foi objeto de descrença por parte de Mendeleev. / This work aims to analyze the concepts of atom and chemical elements, as presented in the writings of the Russian chemist Dmitri I. Mendeleev, (1834 - 1907). In this analysis were used English translations of Mendeleev\"s texts, especially his textbook Principles of Chemistry, but also the papers \"An Attempt to Apply to Chemistry one of The Principles of Newton\'s Natural Philosophy\", (1889) and \"An Attempt Towards a chemical conception of the ether\", (1902). During the nineteenth century, the atomic hypothesis, proposed by Dalton and elaborated by other chemists, was not unanimously accepted by the scientific community. In this context, one may note that Mendeleev was aligned with authors who had reservations about the physical reality of atoms. To understand his reasons, it is important to consider that the first scientific researches performed by Mendeleev were on the so-called indefinite compounds, that is, compounds that did not obey Dalton\"s law of multiple proportions. Mendeleev recognized that the atomic hypothesis explained a series of chemical phenomena, but it could not explain indefinite compounds. Moreover, Mendeleev proposed a clear distinction between the concepts of chemical elements and simple bodies. Elements were abstract entities with chemical individuality, a crucial idea to Mendeleev that led him to the proposition of the periodic law. In the analyzed texts, Mendeleev used, on a recurring basis, the analogy between the solar system and molecules. In this analogy, planets relate to the idea of individuality, which is essential to understand the concept of chemical element, but at the same time does not refer to the idea of physical indivisibility - the point of the atomic hypothesis that has long been subject to disbelief by Mendeleev.

The transit method, employed by Microvariability and Oscillation of Stars (MOST), Kepler, and various ground-based surveys has enabled the characterization of extrasolar planets to unprecedented precision. These results are precise enough to begin to measure planet atmosphere composition, planetary oblateness, starspots, and other phenomena at the level of a few hundred parts per million. However, these results depend on our understanding of stellar limb darkening, that is, the intensity distribution across the stellar disk that is sequentially blocked as the planet transits. Typically, stellar limb darkening is assumed to be a simple parameterization with two coefficients that are derived from stellar atmosphere models or fit directly. In this work, we revisit this assumption and compute synthetic planetary-transit light curves directly from model stellar atmosphere center-to-limb intensity variations (CLIVs) using the plane-parallel Atlas and spherically symmetric SAtlas codes. We compare these light curves to those constructed using best-fit limb-darkening parameterizations. We find that adopting parametric stellar limb-darkening laws leads to systematic differences from the more geometrically realistic model stellar atmosphere CLIV of about 50–100 ppm at the transit center and up to 300 ppm at ingress/egress. While these errors are small, they are systematic, and they appear to limit the precision necessary to measure secondary effects. Our results may also have a significant impact on transit spectra.