Pré-seleção de sítios astronômicos por imagens de satélites meteorológicos

A Astronomia, como origem e, talvez, como fim de todas as Ciências, sempre esteve voltada à observação dos astros e à busca de novas técnicas e instrumentos que permitissem ampliar os limites e a qualidade destas observações. Dessa busca resultou o desenvolvimento do telescópio óptico, em 1608, por Galileu Galilei. Com o passar dos anos, esse instrumento foi sofrendo incontáveis aperfeiçoamentos, chegando aos nossos dias como um aparelho preciso e de sofisticada tecnologia. Apesar das fronteiras observacionais terem avançado para além do espectro visível, o telescópio óptico ainda é indispensável à Astronomia. O Brasil, embora não apresente condições meteorológicas ideais para observações astronômicas, possui observatórios ópticos de razoável qualidade, como o Laboratório Nacional de Astrofísica, LNA, em Minas Gerais, entre outros. Em seu extremo sul, no entanto, o País carece de bons instrumentos ópticos, destacando-se unicamente o telescópio da UFRGS instalado no Observatório do Morro Santana, em Porto Alegre. O aumento da iluminação artificial na Região Metropolitana de Porto Alegre e, conseqüentemente, da claridade do céu noturno tem praticamente inviabilizado a operação do Observatório. Assim, a escolha de novos locais para a futura instalação de telescópios ópticos no Estado é imprescindível. Acrescenta-se a isto o fato do ciclo climático desta região diferenciarse daquele das demais regiões do País, fato relevante, dado que um dos fatores determinantes na escolha de novos sítios para telescópios ópticos é a taxa de nebulosidade. Levantamentos in situ de nebulosidade são longos e custosos. Como alternativa, neste trabalho foi realizado um estudo estatístico do Estado, a partir da montagem de um banco de 472 imagens noturnas dos satélites GOES e MeteoSat. A combinação das imagens, por processo de superposição e cálculo de valores médios de contagens (brilho), à escala de pixel, forneceu informações em nível de préseleção, ou indicativo, de locais com altas taxas de noites claras. Foram cobertos os períodos de 1994-1995 e 1998-1999, com focalização nas áreas em torno de Bom Jesus, Vacaria e Caçapava do Sul. Como controle, foi também monitorada a área em torno do LNA em Minas Gerais. Ademais da demonstração metodológica, os dados orbitais indicaram que, na média destes anos, estas áreas são adequadas à instalação de observatórios astronômicos, pela conjugação dos fatores de nebulosidade e altitude.

Localização de sítios astronômicos através de imagens dos satélites NOAA

Este trabalho se ocupa do problema da localização de sítios adequados para a operação de observatórios astronômicos. O constante crescimento das cidades e a urbanização de grandes áreas vizinhas é acompanhada por um aumento proporcional da iluminação artificial, o que resulta em níveis maiores de brilho do céu noturno. Isto tem consequências extremas para a astronomia óptica, a qual exige um céu escuro, e justifica buscas de novos sítios para a instalação de futuros telescópios ópticos. Um dos critérios mais importantes para sítios astronômicos, além de céu escuro, é uma alta proporção de céu claro, sem nuvens. Buscas de sítios astronômicos são estudos conduzidos ao longo de períodos de tempo de anos. É sugerido que imagens de satélites meteorológicos podem ser úteis para a seleção preliminar destes sítios. A metodologia utilizada é fundamentada em correções geométricas de imagens de dados orbitais das naves NOAA12 e NOAA14 e na soma de imagens obtidas em datas diferentes. As imagens foram coletadas pela estação de recepção instalada no Centro Estadual de Pesquisas em Sensoriamento Remoto e Meteorologia da UFRGS. Somando, pixel por pixel, imagens colhidas em datas diferentes, após correções geométricas, obtém-se médias temporais de cobertura de nuvens, o que é o equivalente moderno da construção de médias a partir de uma série temporal de dados meteorológicos de estações terrestres. Nós demonstramos que esta metodologia é factível para este tipo de dado, originário de órbitas de menor altitude e melhor resolução, se comparado com imagens vindas de satélites de órbitas altas, geoestacionários, com menor resolução, imagens estas de manipulação muito mais fácil, pois o ponto de observação tende a ser estável no tempo.

P22 entrevista: Amâncio Friaça

Entrevista com Amâncio Friaça para a edição 91 da Página 22. Amâncio Friaça é físico, astrônomo e professor associado da USP. Suas áreas de pesquisa são cosmologia, evolução e formação de galáxias, evolução química do Universo, evolução da complexidade no Universo, astrobiologia, transdisciplinaridade e relação entre astronomia e sociedade

A obra de triangulis omnimodis libri quinque de Johann Müller Regiomontanus (1436 1476): uma contribuição para o desenvolvimento da trigonometria

Trigonometry, branch of mathematics related to the study of triangles, developed from practical needs, especially relating to astronomy, Surveying and Navigation. Johann Müller, the Regiomontanus (1436-1476) mathematician and astronomer of the fifteenth century played an important role in the development of this science. His work titled De Triangulis Omnimodis Libri Quinque written around 1464, and published posthumously in 1533, presents the first systematic exposure of European plane and spherical trigonometry, a treatment independent of astronomy. In this study we present a description, translation and analysis of some aspects of this important work in the history of trigonometry. Therefore, the translation was performed using a version of the book Regiomontanus on Triangles of Barnabas Hughes, 1967. In it you will find the original work in Latin and an English translation. For this study, we use for most of our translation in Portuguese, the English version, but some doubt utterance, statement and figures were made by the original Latin. In this work, we can see that trigonometry is considered as a branch of mathematics which is subordinated to geometry, that is, toward the study of triangles. Regiomontanus provides a large number of theorems as the original trigonometric formula for the area of a triangle. Use algebra to solve geometric problems and mainly shows the first practical theorem for the law of cosines in spherical trigonometry. Thus, this study shows some of the development of the trigonometry in the fifteenth century, especially with regard to concepts such as sine and cosine (sine reverse), the work discussed above, is of paramount importance for the research in the history of mathematics more specifically in the area of historical analysis and critique of literary sources or studying the work of a particular mathematician

A leitura de fontes antigas como possibilidade didatica: um exemplo a partir do Almagesto de Ptolomeu

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Saberes ambientais e estações do ano

La enseñanza de las estaciones es fundamental para la comprensión de muchos ciclos naturales de la Tierra y, por consiguiente, debe integrar una educación en astronomía comprometidos con una educación ambiental más amplio. Sin embargo, la literatura en la educación científica ha puesto de manifiesto durante mucho tiempo la existencia de asociaciones erróneas de las estaciones astronómicas con características contradictorias de los ambientes que experimentamos en nuestro país. Los estudios de los autores de la historia de la astronomía y la astronomía cultural sugieren que la corrección de este error requiere la sistematización de los conocimientos sobre el comportamiento anual del medio ambiente local y, al mismo tiempo, la comprensión de los diferentes puntos de vista en el que las estaciones estaban y se cree por diferentes culturas, en particular, pero sin limitarse, a la perspectiva que utiliza como referencia el movimiento anual del Sol como base para la división del año en cuatro estaciones. Agregado a la reflexión sobre el enfoque humanista a la enseñanza de la astronomía, estos estudios sirvieron de base para la realización de investigaciones con los pescadores de la playa de Ponta Negra, durante los meses de mayo, junio y julio de 2012 y mayo-agosto en 2013; con el fin de conocer sus percepciones sobre el ambiente de la playa e investigar las posibles referencias que tienen del cielo durante el año. Más allá de la contextualización y reflexiones desarrolladas en la tesis, se presentan como un producto de la investigación el material educativo que consiste en el video "Las estaciones del mar de Ponta Negra" para ser utilizado como apoyo en talleres o cursos para estudiantes universitarios y profesores, que implica el tema de las estaciones . El material se utiliza la percepción de los pescadores en la playa dirigidas a contribuir así al diálogo entre la ciencia y el conocimiento cotidiano, y para reducir la brecha del conocimiento sistematizado sobre las características y los cambios anuales en el entorno de Natal / RN, en particular en el contexto de la enseñanza de las Ciencias. Al mismo tiempo, se espera favorecer la mirada del los profesores y futuros profesores para el medio ambiente local y la variedad que las diferentes culturas perciben los ciclos anuales y sus entornos

Uma análise teórica da evolução da rotação estelar

In the past 50 years, large efforts have been made toward the understanding of the stellar evolution. In the observational context, large sets of precise measurements of projected rotational velocity were produced, in particular by the Natal and Geneva groups. From these data, it is now possible to establish the behavior of stellar rotation from the turnoff to the red giant branch. In addition, these data have shown the role of tidal effects on stellar rotation in close binary systems. Nevertheless, relatively little attention has been paid to theoretical studies on the evolution of rotation along the HR Diagram, a topic itself directly associated to the evolution of the stars. Basically, there are two reasons for such a fact, (i) spherical symmetry is not assumed, what leads to a substantial increase in the numerical complexity of equations and (ii) non rotating models have been very successful in explaining relevant observational data, including the mass-luminosity relation and chemical abundances. In spite of these facts, it is clear that considerable work remains to be done on the role of rotation in the later stages of the evolution, where clear disagreements arise from confrontations between theoretical predictions and observations. In the present work we study the evolutionary behavior of stellar rotation along the HR Diagram, taking into account constraint conditions issued from recent observational survey of rotational velocity carried out with high precision procedures and new evolutionary codes

Modelos analíticos para rádio fontes extragalácticas

The great majority of analytical models for extragalactic radio sources suppose self-similarity and can be classified into three types: I, II and III. We have developed a model that represents a generalization of most models found in the literature and showed that these three types are particular cases. The model assumes that the area of the head of the jet varies with the jet size according to a power law and the jet luminosity is a function of time. As it is usually done, the basic hypothesis is that there is an equilibrium between the pressure exerted both by the head of the jet and the cocoon walls and the ram pressure of the ambient medium. The equilibrium equations and energy conservation equation allow us to express the size and width of the source and the pressure in the cocoon as a power law and find the respective exponents. All these assumptions can be used to calculate the evolution of the source size, width and radio luminosity. This can then be compared with the observed width-size relation for radio lobes and the power-size (P-D) diagram of both compact (GPS and CSS) and extended sources from the 3CR catalogue. In this work we introduce two important improvement as compared with a previous work: (1)We have put together a larger sample of both compact and extended radio sources

A evolução do lítio em estrelas do tipo-solar através do diagrama HR

Important advances have been made along the last decade in the study of the lithium behavior in solar-type stars. Among the most important discoveries what attracts attention is that the distribution of lithium abundance in the late F-type giant stars tends to be discontinuous, at the same time of a sudden decline in rotation and a gradual decline according to the temperature for giant red stars of such spectral type. Other studies have also shown that synchronized binary systems with evolved components seem to keep more of their original lithium than the unsynchronized systems. evertheless, the connection between rotation and lithium abundance as well as the role of tidal effects on lithium dilution seem to be more complicated matters, depending on mass, metallicity and age. This work brings an unprecedented study about the behavior of lithium abundance in solartype evolved stars based on an unique sample of 1067 subgiant, giant and supergiant stars, 236 of them presenting spectroscopic binary characteristics, with precise lithium abundance and projected rotational speed. Now the lithium-rotation connection for single and binary evolved stars is analyzed taking into account the role of mass and stellar age

Acelaração do universo e criação gravitacional de matéria escura fria: novos modelos e testes observacionais

Recent astronomical observations (involving supernovae type Ia, cosmic background radiation anisotropy and galaxy clusters probes) have provided strong evidence that the observed universe is described by an accelerating, flat model whose space-time properties can be represented by the FriedmannRobertsonWalker (FRW) metric. However, the nature of the substance or mechanism behind the current cosmic acceleration remains unknown and its determination constitutes a challenging problem for modern cosmology. In the general relativistic description, an accelerat ing regime is usually obtained by assuming the existence of an exotic energy component endowed with negative pressure, called dark energy, which is usually represented by a cosmological constant ¤ associated to the vacuum energy density. All observational data available so far are in good agreement with the concordance cosmic ¤CDM model. Nevertheless, such models are plagued with several problems thereby inspiring many authors to propose alternative candidates in the relativistic context. In this thesis, a new kind of accelerating flat model with no dark energy and fully dominated by cold dark matter (CDM) is proposed. The number of CDM particles is not conserved and the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational particle creation. In order to have a transition from a decelerating to an accelerating regime at low redshifts, the matter creation rate proposed here depends on 2 parameters (y and ߯): the first one identifies a constant term of the order of H0 and the second one describes a time variation proportional to he Hubble parameter H(t). In this scenario, H0 does not need to be small in order to solve the age problem and the transition happens even if there is no matter creation during the radiation and part of the matter dominated phase (when the ß term is negligible). Like in flat ACDM scenarios, the dimming of distant type Ia supernovae can be fitted with just one free parameter, and the coincidence problem plaguing the models driven by the cosmological constant. ACDM is absent. The limits endowed with with the existence of the quasar APM 08279+5255, located at z = 3:91 and with an estimated ages between 2 and 3 Gyr are also investigated. In the simplest case (ß = 0), the model is compatible with the existence of the quasar for y > 0:56 whether the age of the quasar is 2.0 Gyr. For 3 Gyr the limit derived is y > 0:72. New limits for the formation redshift of the quasar are also established

Estudo sistemático de estrelas variáveis na era dos grandes surveys

The interest in the systematic analysis of astronomical time series data, as well as development in astronomical instrumentation and automation over the past two decades has given rise to several questions of how to analyze and synthesize the growing amount of data. These data have led to many discoveries in the areas of modern astronomy asteroseismology, exoplanets and stellar evolution. However, treatment methods and data analysis have failed to follow the development of the instruments themselves, although much effort has been done. In present thesis, we propose new methods of data analysis and two catalogs of the variable stars that allowed the study of rotational modulation and stellar variability. Were analyzed the photometric databases fromtwo distinctmissions: CoRoT (Convection Rotation and planetary Transits) and WFCAM (Wide Field Camera). Furthermore the present work describes several methods for the analysis of photometric data besides propose and refine selection techniques of data using indices of variability. Preliminary results show that variability indices have an efficiency greater than the indices most often used in the literature. An efficient selection of variable stars is essential to improve the efficiency of all subsequent steps. Fromthese analyses were obtained two catalogs; first, fromtheWFCAMdatabase we achieve a catalog with 319 variable stars observed in the photometric bands Y ZJHK. These stars show periods ranging between ∼ 0, 2 to ∼ 560 days whose the variability signatures present RR-Lyrae, Cepheids , LPVs, cataclysmic variables, among many others. Second, from the CoRoT database we selected 4, 206 stars with typical signatures of rotationalmodulation, using a supervised process. These stars show periods ranging between ∼ 0, 33 to ∼ 92 days, amplitude variability between ∼ 0, 001 to ∼ 0, 5 mag, color index (J - H) between ∼ 0, 0 to ∼ 1, 4 mag and spectral type CoRoT FGKM. The WFCAM variable stars catalog is being used to compose a database of light curves to be used as template in an automatic classifier for variable stars observed by the project VVV (Visible and Infrared Survey Telescope for Astronomy) moreover it are a fundamental start point to study different scientific cases. For example, a set of 12 young stars who are in a star formation region and the study of RR Lyrae-whose properties are not well established in the infrared. Based on CoRoT results we were able to show, for the first time, the rotational modulation evolution for an wide homogeneous sample of field stars. The results are inagreement with those expected by the stellar evolution theory. Furthermore, we identified 4 solar-type stars ( with color indices, spectral type, luminosity class and rotation period close to the Sun) besides 400 M-giant stars that we have a special interest to forthcoming studies. From the solar-type stars we can describe the future and past of the Sun while properties of M-stars are not well known. Our results allow concluded that there is a high dependence of the color-period diagram with the reddening in which increase the uncertainties of the age-period realized by previous works using CoRoT data. This thesis provides a large data-set for different scientific works, such as; magnetic activity, cataclysmic variables, brown dwarfs, RR-Lyrae, solar analogous, giant stars, among others. For instance, these data will allow us to study the relationship of magnetic activitywith stellar evolution. Besides these aspects, this thesis presents an improved classification for a significant number of stars in the CoRoT database and introduces a new set of tools that can be used to improve the entire process of the photometric databases analysis

Efeitos das inomogeneidades da matéria em Cosmologias Aceleradas

The recent observational advances of Astronomy and a more consistent theoretical framework turned Cosmology in one of the most exciting frontiers of contemporary science. In this thesis, homogeneous and inhomogeneous Universe models containing dark matter and different kinds of dark energy are confronted with recent observational data. Initially, we analyze constraints from the existence of old high redshift objects, Supernovas type Ia and the gas mass fraction of galaxy clusters for 2 distinct classes of homogeneous and isotropic models: decaying vacuum and X(z)CDM cosmologies. By considering the quasar APM 08279+5255 at z = 3.91 with age between 2-3 Gyr, we obtain 0,2 < OM < 0,4 while for the j3 parameter which quantifies the contribution of A( t) is restricted to the intervalO, 07 < j3 < 0,32 thereby implying that the minimal age of the Universe amounts to 13.4 Gyr. A lower limit to the quasar formation redshift (zJ > 5,11) was also obtained. Our analyzes including flat, closed and hyperbolic models show that there is no an age crisis for this kind of decaying A( t) scenario. Tests from SN e Ia and gas mass fraction data were realized for flat X(z)CDM models. For an equation of state, úJ(z) = úJo + úJIZ, the best fit is úJo = -1,25, úJl = 1,3 and OM = 0,26, whereas for models with úJ(z) = úJo+úJlz/(l+z), we obtainúJo = -1,4, úJl = 2,57 and OM = 0,26. In another line of development, we have discussed the influence of the observed inhomogeneities by considering the Zeldovich-Kantowski-DyerRoeder (ZKDR) angular diameter distance. By applying the statistical X2 method to a sample of angular diameter for compact radio sources, the best fit to the cosmological parameters for XCDM models are OM = O, 26,úJ = -1,03 and a = 0,9, where úJ and a are the equation of state and the smoothness parameters, respectively. Such results are compatible with a phantom energy component (úJ < -1). The possible bidimensional spaces associated to the plane (a , OM) were restricted by using data from SNe Ia and gas mass fraction of galaxy clusters. For Supernovas the parameters are restricted to the interval 0,32 < OM < 0,5(20") and 0,32 < a < 1,0(20"), while to the gas mass fraction we find 0,18 < OM < 0,32(20") with alI alIowed values of a. For a joint analysis involving Supernovas and gas mass fraction data we obtained 0,18 < OM < 0,38(20"). In general grounds, the present study suggests that the influence of the cosmological inhomogeneities in the matter distribution need to be considered with more detail in the analyses of the observational tests. Further, the analytical treatment based on the ZKDR distance may give non-negligible corrections to the so-calIed background tests of FRW type cosmologies

Sobre a relação entre rotação, atividade crosmosférica e abundância de lítio em estrelas subgigantes

The connection between rotation, CaII emission flux and lithium abundance is analyzed for a sample of subgiant stars, with evolutionary status was determined from the Toulouse-Geneve code and HlPPARCOS trigonometric parallax measurements. We noted that the distribution of rotation and CaII emission flux, as a function of effective temperature, shows a discontinuity located around the same spectral type, F8IV. Stars located blueward of this spectral type, exhibit a large spread of values of rotation and CaII flux, whereas stars redward of F8lV show essentially low ratation anel low CaII flux. The strength of these declines nevertheless, depends on stellar mass. The distribution of lithium abundances also shows a discontinuity, however with behavior a little more complex for subgiants with mass lower than about 1.2 Solar Masses, this decrease is observed later than that in rotation and CaII flux, whereas for masses higher than 1.2 Solar Masses the decrease in lithium abundance is located around the spectral type F8IV. The discrepancy between the location of the discontinuities of rotation and CaII flux and log n(Li) for stars with masses lower than 102 Solar Masses, seems to reflect the sensitivity of these phenomena to the mass of the convective envelope. The drop in rotation, which results mostly from a magnetic braking, requires an increase in the mass of the convective envelope less than that required for the decrease in lithium abundance The location of the discontinuity in log n( Li) in the same region of the discontinuity ties in rotation and CaII flux, for stars with masses higher than 1.2 Solar Masses, may also be explained by the behavior of the deepening of the convective envelope. In contrast to the relationship between rotation and CaII flux the relationship between lithium abundance and rotation shows no dear tendency toward linear behavior. Similarly, the same tendency is observed in the relationship between lithium abundance and CaII flux in spite of these facts, subgiants with high lithium content also have high rotation and high CaII emission flux. We also observed that stars with high lithium content present, in its majority, an undeveloped convective envelope, whereas stars with low lithium content have a developed convective envelope. In the case of the rotation, stars with undeveloped convective envelope, show rotational velocities as much high as low, whereas stars with developed convective envelope only present low rotation

Evolução de estruturas primordiais

Understanding the way in which large-scale structures, like galaxies, form remains one of the most challenging problems in cosmology today. The standard theory for the origin of these structures is that they grew by gravitational instability from small, perhaps quantum generated, °uctuations in the density of dark matter, baryons and photons over an uniform primordial Universe. After the recombination, the baryons began to fall into the pre-existing gravitational potential wells of the dark matter. In this dissertation a study is initially made of the primordial recombination era, the epoch of the formation of the neutral hydrogen atoms. Besides, we analyzed the evolution of the density contrast (of baryonic and dark matter), in clouds of dark matter with masses among 104M¯ ¡ 1010M¯. In particular, we take into account the several physical mechanisms that act in the baryonic component, during and after the recombination era. The analysis of the formation of these primordial objects was made in the context of three models of dark energy as background: Quintessence, ¤CDM(Cosmological Constant plus Cold Dark Matter) and Phantom. We show that the dark matter is the fundamental agent for the formation of the structures observed today. The dark energy has great importance at that epoch of its formation

Abordando o ensino de óptica através da construção de telescópios

A proposta deste trabalho é a construção artesanal de um telescópio refletor do tipo Newtoniano relacionando conteúdos abordados na disciplina de óptica, como a formação de imagens em lentes e espelhos, aberrações esféricas e cromáticas, interferência e difração, com cada fase do processo de construção. Com o aparelho construído é possível abordar a fotografia lunar e planetária com alta resolução e sua utilização por alunos do curso de Licenciatura em Física já demonstra ser um grande incentivo à contemplação do céu e à compreensão de muitos fenômenos físicos, com ocorrências de eclipses, formação das marés, estações do ano, etc, que geralmente são pouco abordados nas escolas de Ensino Fundamental e Médio. de acordo com diagnóstico realizado pelos alunos de graduação em algumas escolas do município de Bauru, verificou-se que a única abordagem de astronomia é apenas em relação ao sistema solar, especificamente órbitas planetárias, nas disciplinas de Física ou Geografia. Além do telescópio, a utilização de animações produzidas por alunos de graduação também pode ser considerada como uma ferramenta eficiente no ensino de astronomia, principalmente para alunos de Ensino Fundamental.