Impact flux of asteroids and water transport to the habitable zone in binary star systems

By now, observations of exoplanets have found more than 50 binary star systems hosting 71 planets. We expect these numbers to increase as more than 70% of the main sequence stars in the solar neighborhood are members of binary or multiple systems. The planetary motion in such systems depends strongly on both the parameters of the stellar system (stellar separation and eccentricity) and the architecture of the planetary system (number of planets and their orbital behaviour). In case a terrestrial planet moves in the so-called habitable zone (HZ) of its host star, the habitability of this planet depends on many parameters. A crucial factor is certainly the amount of water. We investigate in this work the transport of water from beyond the snow-line to the HZ in a binary star system and compare it to a single star system

Asteroid flux towards circumprimary habitable zones in binary star systems: I. Statistical Overview

So far, multiple stellar systems harbor more than 130 extra solar planets. Dynamical simulations show that the outcome of planetary formation process can lead to various planetary architecture (i.e. location, size, mass and water content) when the star system is single or double. In the late phase of planetary formation, when embryo-sized objects dominate the inner region of the system, asteroids are also present and can provide additional material for objects inside the habitable zone (hereafter HZ). In this study, we make a comparison of several binary star systems and their efficiency to move icy asteroids from beyond the snow-line into orbits crossing the HZ. We modeled a belt of 10000 asteroids (remnants from the late phase of planetary formation process) beyond the snow-line. The planetesimals are placed randomly around the primary star and move under the gravitational influence of the two stars and a gas giant. As the planetesimals do not interact with each other, we divided the belt into 100 subrings which were separately integrated. In this statistical study, several double star configurations with a G-type star as primary are investigated. Our results show that small bodies also participate in bearing a non-negligible amount of water to the HZ. The proximity of a companion moving on an eccentric orbit increases the flux of asteroids to the HZ, which could result into a more efficient water transport on a short timescale, causing a heavy bombardment. In contrast to asteroids moving under the gravitational perturbations of one G-type star and a gas giant, we show that the presence of a companion star can not only favor a faster depletion of our disk of planetesimals but can also bring 4 -- 5 times more water into the whole HZ.Comment: Accepted for publication in A&

Second Harmonic Generation imaging of collagen fibrillogenesis

International audienceDevelopment of nonlinear optical microscopy has significantly improved three-dimensional (3D) imaging of biological tissues in recent years. In particular, collagen has been shown to exhibit endogenous Second Harmonic Generation (SHG) signals and SHG microscopy has proved to enable the visualization of collagen architecture in tissues with unequalled contrast and specificity [1, 2]. Type I collagen is a major structural protein in mammals and shows highly structured macromolecular organizations specific to each tissue. It is synthesized by cells as triple helices, which self-assemble outside the cells into fibrils that further form fibers, lamellae or other three-dimensional (3D) networks. This assembly mechanism depends critically on the collagen concentration, as well as on the temperature, pH and ionic strength of the solution in vitro. Thorough characterization of collagen fibrillogenesis is crucial to understand the biological mechanisms of tissue formation and tissue remodeling in response to a variety of pathologies. Booming of tissue engineering furthermore requires advanced in situ quantitative imaging techniques to verify whether the tissue substitutes display appropriate biomimetic 3D organization for cell culture scaffolds or functional implants. In this study, we continuously monitored the formation of collagen fibrils by time-lapse SHG microscopy [3]. Fibrillogenesis was triggered in a controlled way by increasing the pH in a dilute solution of collagen I. The fibril density was measured every 10 to 20 minutes as the number of voxels with significant SHG signal in 3D image stacks [1]. Our results showed reproducible dynamics of fibrillar collagen formation that could be changed by tuning the pH (see figure 1). We also monitored the growth of single fibrils and measured the length increase over time, which had never been reported before using an optical technique. We then correlated these SHG images to TEM images at nanometer-scale resolution by blocking the fibrillogenesis at early stages and drying the samples. It showed that SHG microscopy allows imaging of fibrils with a diameter down to 30-50 nm in our experimental conditions. We finally investigated surface-mediated fibrillogenesis by adding silica nanoparticles to the solution [4]. We used Two-Photon excited fluorescence (2PEF) microscopy to visualize the fluorescently-died nanoparticles and quantify the self-assembly of collagen around these nanoparticles. In conclusion, SHG microscopy enabled sensitive and well contrasted 3D visualization of collagen fibrillogenesis in a non invasive way. This work illustrates the potential of SHG microscopy for the rational design and characterization of collagen-based biomaterials. 0 200 400 600 800 0.0 0.5 1.0 1.5 2.0 2.5 Pixel fraction (%) Time (min) (d) (a) (c) (b) Fig 1. 3D reconstruction of SHG images of collagen fibrillogenesis (at pH=6.5) after a) 170 b) 410 and c) 730 minutes; d) Experimental kinetics of fibril density in the SHG images (black dots) with exponential fitting (red line). References [1] M

The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis

Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO . The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids.Comment: Accepted for publication in A&

Fast spectrally encoded Mueller optical scanning microscopy

Mueller microscopes enable imaging of the optical anisotropic properties of biological or non-biological samples, in phase and amplitude, at sub-micrometre scale. However, the development of Mueller microscopes poses an instrumental challenge: the production of polarimetric parameters must be sufficiently quick to ensure fast imaging, so that the evolution of these parameters can be visualised in real-time, allowing the operator to adjust the microscope while constantly monitoring them. In this report, a full Mueller scanning microscope based on spectral encoding of polarization is presented. The spectrum, collected every 10 μs for each position of the optical beam on the specimen, incorporates all the information needed to produce the full Mueller matrix, which allows simultaneous display of all the polarimetric parameters, at the unequalled rate of 1.5 Hz (for an image of 256 × 256 pixels). The design of the optical blocks allows for the real-time display of linear birefringent images which serve as guidance for the operator. In addition, the instrument has the capability to easily switch its functionality from a Mueller to a Second Harmonic Generation (SHG) microscope, providing a pixel-to-pixel matching of the images produced by the two modalities. The device performance is illustrated by imaging various unstained biological specimens

The astrometric Gaia-FUN-SSO observation campaign of 99942 Apophis

© 2015 ESO. Aims. Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO. Methods. The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center. Results. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids

Impact flux of asteroids and water transport to the habitable zone in binary star systems

International audienceBy now, observations of exoplanets have found more than 50 binary star systems hosting 71 planets. We expect these numbers to increase as more than 70% of the main sequence stars in the solar neighborhood are members of binary or multiple systems. The planetary motion in such systems depends strongly on both the parameters of the stellar system (stellar separation and eccentricity) and the architecture of the planetary system (number of planets and their orbital behaviour). In case a terrestrial planet moves in the so-called habitable zone (HZ) of its host star, the habitability of this planet depends on many parameters. A crucial factor is certainly the amount of water. We investigate in this work the transport of water from beyond the snow-line to the HZ in a binary star system and compare it to a single star system

NEOPROP: a NEO Propagator for Space Situational Awareness, IAA-PDC13-05-03P (poster session)

International audienc

NEOPROP: a NEO Propagator for Space Situational Awareness, IAA-PDC13-05-03P (poster session)

International audienc

NEOPROP: a NEO Propagator for Space Situational Awareness, IAA-PDC13-05-03P (poster session)

International audienc