Morfologia em alta resolução espacial de estrelas de tipo Mira e R Corenae Borealis

Mira and R Coronae Borealis (R CrB) variable stars are evolved objects surrounded by circumstellar envelopes (CSE) composed of the ejected stellar material. We present a detailed high-spatial resolution morfological study of the CSE of three stars: IRC+10216, the closest and more studied Carbon-Rich Mira; o Ceti, the prototype of the Mira class; and RY Sagitarii (RY Sgr), the brightest R CrB variable of the south hemisphere. JHKL near-infrared adaptive optics images of IRC+10216 with high dynamic range and Vband images with high angular resolution and high depth, collected with the VLT/NACO and VLT/FORS1 instruments, were analyzed. NACO images of o Ceti were also analyzed. Interferometric observations of RY Sgr collected with the VLTI/MIDI instrument allowed us to explore its CSE innermost regions (»20 40 mas). The CSE of IRC+10216 exhibit, in near-infrared, clumps with more complex relative displacements than proposed in previous studies. In V-band, the majority of the non-concentric shells, located in the outer CSE layers, seem to be composed of thinner elongated shells. In a global view, the morphological connection between the shells and the bipolar core of the nebulae, located in the outer layers, together with the clumps, located in the innermost regions, has a difficult interpretation. In the CSE of o Ceti, preliminar results would be indicating the presence of possible clumps. In the innermost regions (.110 UA) of the CSE of RY Sgr, two clouds were detected in different epochs, embedded in a variable gaussian envelope. Based on a rigorous verification, the first cloud was located at »100 R¤ (or »30 AU) from the centre, toward the east-north-east direction (modulo 180o) and the second one was almost at a perpendicular direction, having aproximately 2£ the distance of the first cloud. This study introduces new constraints to the mass-loss history of these kind of variables and to the morphology of their innermost CSE regions

Inércia e Natureza da Ciência no Ensino de Física: uma sequência didática centrada no desenvolvimento histórico do conceito de inércia

During the last decades the area of science education has discussed issues related to the inclusion of the History and Philosophy of Science (HFS) in the practice of science teaching. Among the arguments put forward in favour of this approach, it is pointed out the possible enhancement of scientific content learning and the understanding of the nature of Science (NoS). In spite of such considerations, we still have a very small number of research papers reporting results of practical interventions that utilize the historical approach, moreover, there is a lack of teaching materials in this perspective. Our work has sought to contribute to this area with regard to two aspects: on the one hand, with the production of didactic material, by drawing up texts on the history of inertia for graduate students. On the other hand, we investigate whether the arguments mentioned above in relation to the didactic use of HFS sustain themselves, in a particular context. We developed and applied a didactic sequence, using the texts that we built, to teach the concept of inertia and discuss selected contents of NoS. The didactic sequence was applied in two graduate classes, one from a course of Geophysics (BSc.) and another from the Physics (teaching formation), both from the Federal University of Rio Grande do Norte (UFRN). An initial survey exposed that students, even having approached the concept of inertia in basic education, presented conceptions of common sense regarding the relationship between force and motion. The questionnaire also allowed us to identify the existence of elements of concepts considered inadequate as regards to NoS. At the end of our research, our data indicated a greater number of positive hits on the issues concerning the concept of inertia. Regarding the aspects of NoS, we were able to identify, in a few cases, a move towards a more appropriate understanding, however, certain distortions persisted, highlighting the limitations of the approach used