High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood (d a parts per thousand currency signaEuro parts per thousand 15 pc) with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT-the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements at the 0.05 mu as (1 sigma) accuracy level, sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope (D = 1 m), a detector with a large field of view located 40 m away from the telescope and made of 8 small movable CCDs located around a fixed central CCD, and an interferometric calibration system monitoring dynamical Young's fringes originating from metrology fibers located at the primary mirror. The mission profile is driven by the fact that the two main modules of the payload, the telescope and the focal plane, must be located 40 m away leading to the choice of a formation flying option as the reference mission, and of a deployable boom option as an alternative choice. The proposed mission architecture relies on the use of two satellites, of about 700 kg each, operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations. The two satellites will be launched in a stacked configuration using a Soyuz ST launch vehicle. The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits each distributed over the nominal mission duration. The main survey operation will use approximately 70% of the mission lifetime. The remaining 30% of NEAT observing time might be allocated, for example, to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys, and other programs. With its exquisite, surgical astrometric precision, NEAT holds the promise to provide the first thorough census for Earth-mass planets around stars in the immediate vicinity of our Sun.

Acesso à educação infantil e trajetórias de desempenho escolar no ensino fundamental

No pressuposto de que a educação infantil (EI) contribui para trajetórias escolares mais favoráveis, o objetivo deste estudo foi verificar o impacto do tempo de exposição à educação infantil sobre o desempenho acadêmico e avaliar o progresso escolar das crianças, na trajetória do 3º ao 5º ano do ensino fundamental, em função da exposição à educação infantil. Participaram 294 alunos de escolas públicas, reunidos em três grupos: sem EI, com um ano de EI e com dois anos de EI. Avaliou-se o desempenho no 3º, 4º e 5º anos, por meio do julgamento do professor e provas coletivas. O Teste de Desempenho Escolar foi aplicado no 3º e 5º ano. Controlado o efeito do nível socioeconômico, a análise de variância com medidas repetidas mostrou que o acesso à EI foi consistentemente associado a melhor desempenho, porém um tempo maior de exposição à EI não teve efeito adicional. Dadas suas implicações para políticas públicas, este último resultado requer verificação e esclarecimento por meio de novas pesquisas.