Após o desenvolvimento do Modelo Padrão da Cosmologia, o Modelo do Big Bang, ao que tudo indicava, havia-se construído uma teoria satisfatória capaz de descrever a evolução do Universo a partir de um estado quente e denso inicial. No entanto, algumas questões em aberto levaram à proposta do modelo da Inflação Cosmológica, o qual descreve uma expansão acelerada no Universo antigo que teria durado uma fração de segundo, e após a qual o Universo teria seguido sua expansão conforme previsto pelo Modelo do \textit{Big Bang}. Embora hoje existam alternativas à Inflação que são capazes de resolver as mesmas questões, a Inflação foi a primeira teoria com a qual foi possível se fazer previsões consistentes sobre a estrutura do Universo em larga escala, como a distribuição de galáxias, aglomerados etc., ao fornecer uma descrição para a origem das mesmas. Neste artigo será apresentado o Modelo Inflacionário, desde uma perspectiva histórica e também matemática. Serão abordadas as críticas e desafios que acercam este modelo atualmente e também as perspectivas futuras no que se refere a testes do modelo inflacionário com os novos experimentos.
Apresentamos neste artigo um panorama da nucleossíntese cosmológica, estelar e catastrófica que leva a povoar a Tabela Periódica do elementos criada por D. Mendeleev há mais de um século.
Desde tempos imemoriais que os seres humanos olham e tentam perceber o céu. Não sabiam bem o que eram aquelas luzes a brilhar e que se movimentavam de forma repetida. Hoje em dia parece muito fácil, mas demorou muito tempo a consolidar-se a imagem que atualmente temos do céu. E sobretudo, a sabermos qual era a sua composição química. Este artigo pretende fazer uma revisão de divulgação do conhecimento químico que temos do céu e mostrar que as informações químicas são indissociáveis do entendimento que temos hoje do universo.
Neste artigo explicamos o que são as ondas gravitacionais previstas pela teoria da relatividade geral de Einstein, falamos de suas fontes astrofísicas e cosmológicas e dos detectores que foram utilizados para a sua busca. Completamos o artigo com a menção aos detectores futuros, que estão sendo projetados para dar uma nova dimensão à astronomia de ondas gravitacionais e à astronomia multimensageira envolvendo ondas gravitacionais.
Discuto alguns aspectos do chamado “paradigma da luz cansada”, o qual representa uma das possíveis explicações para a dependência do desvio espectral para o vermelho de uma fonte cósmica distante com a sua distância até o observador. A mais popular representação fenomenológica do paradigma é apresentada em algum detalhe. Além disso, sendo o processo físico responsável pelo hipotético fenômeno ainda desconhecido, apresento também uma sugestão para a sua descoberta.
O objetivo deste artigo é mostrar o motivo de se considerar a matéria escura como ingrediente fundamental para o Universo. A existência da matéria escura é indispensável para formar as estruturas cósmicas que observamos como galáxias e aglomerados de galáxias. Apesar de ainda desconhecermos a natureza desta componente cósmica, pois ainda não a detectamos diretamente, o aspecto discutido neste trabalho é considerado um dos principais argumentos a favor da existência da matéria escura.
This paper is a refutation of two researches by A. N. Sazonov on HZ Her and V1341 Cyg published in the Astronomy Reports (Vol. 55, p.p.142 and 230) in 2011. We analyzed his photometry along with other data collected in the literature and Internet. The observations of Sazonov are fake and are not related to real stars. Conclusions contained in his papers do not constitute any scientific value. We describe the properties of these two objects, derived from real observations. The following papers based on the same fake observations and published by him in astro-ph arXiv:0904.0168, arXiv:0907.3822, arXiv:0912.0706, arXiv:1011.3980, and arXiv:1102.0379 are also inauthentic.
Recently Block published an astro-ph{{this http URL (2011).}} insinuating that Lemaitre discovery paper of the Expanding Universe was censored prior to its translation into English and publication in the Monthly Notices of the Royal Astronomical Society. Consequently, Lemaitre's credit for the discovery of the velocity-distance correlation was not recognized. We examine here the chain of events leading to the discovery of the 'Hubble law'. Our summary: (a) Lemaitre found a theoretical linear correlation between velocity and distance. (b) Lemaitre assumed the existence of a linear relation between velocity and distance and calculated the coefficient. (c) Hubble took the data plotted it and demonstrated that a linear relation represents the observed data. (d) Hubble never believed in Lemaitre's solution, namely in an expanding universe. Consequently, Hubble never cited Lemaitre. We conclude that the charge that Lemaitre's paper was censored or ignored let alone plagiarized by Hubble, is not founded, and explain why Lemaitre's earlier theoretical discovery and derived 'Hubble constant' was not cited or recognized, by Hubble as well as by many other leading researchers.
We develop a new Bayesian method for estimating white noise levels in CMB sky maps, and apply this algorithm to the five-year Wilkinson Microwave Anisotropy Probe (WMAP) data. We assume that the amplitude of the noise rms is scaled by a constant value, α, relative to a pre-specified noise level. We then derive the corresponding conditional density, P(α | s, Cℓ, d), which is subsequently integrated into a general CMB Gibbs sampler. We first verify our code by analyzing simulated data sets, and then apply the framework to the WMAP data. For the foreground-reduced five-year WMAP sky maps and the nominal noise levels initially provided in the five-year data release, we find that the posterior means typically range between α = 1.005 ± 0.001 and α = 1.010 ± 0.001 depending on differencing assembly, indicating that the noise level of these maps are biased low by 0.5%–1.0%. The same problem is not observed for the uncorrected WMAP sky maps. After the preprint version of this letter appeared on astro-ph., the WMAP team has corrected the values presented on their web page, noting that the initially provided values were in fact estimates from the three-year data release, not from the five-year estimates. However, internally in their five-year analysis the correct noise values were used, and no cosmological results are therefore compromised by this error. Thus, our method has already been demonstrated in practice to be both useful and accurate.
In a previous paper (Falkenberg, Kotulla & Fritze 2009, astro-ph/0901.1665) we have shown that the classical definition of E+A galaxies excludes a significant number of post-starburst galaxies. We suggested that analysing broad-band spectral energy distributions (SEDs) is a more comprehensive method to select and distinguish poststarburst galaxies than the classical definition of measuring equivalent widths of (Hδ) and [O ii] lines. In this paper we will carefully investigate this new method and evaluate it by comparing our model grid of post-starburst galaxies to observed E+A galaxies from the MORPHS catalog. In a first part we investigate the UV/U-optical-NIR SEDs of a large variety in terms of progenitor galaxies, burst strengths and timescales of post-starburst models and compare them to undisturbed spiral, S0 and E galaxies as well as to galaxies in their starburst phase. In a second part we compare our post-starburst models with the observed E+A galaxies in terms of Lick indices, luminosities and colours. We then use the new method of comparing the model SEDs with SEDs of the observed E+A galaxies. We find that the post-starburst models can be distinguished from undisturbed spiral, S0 and E galaxies and galaxies in their starburst phase on the basis of their SEDs. It is even possible to distinguish most of the different post-starburst by their SEDs. From the comparison with observations we find that all observed E+A galaxies from the MORPHS catalog can be matched by our models. However only models with short decline timescales for the star formation rate are possible scenarios for the observed E+A galaxies in agreement with our results from the first paper (see Falkenberg, Kotulla & Fritze 2009a).
Practical expressions are derived for a rapid and accurate evaluation of electric and thermal conductivities and thermopower of degenerate relativistic electrons along quantizing magnetic fields in outer neutron star crusts. The electron Coulomb scattering on ions is considered in liquid matter, and on high-temperature phonons or charged impurities in solid matter. A semi-quantitative treatment of low-temperature phonons is also proposed. The transport properties are expressed through the energy dependent effective electron relaxation time, which is calculated using the theoretical formalism of the previous work (astro-ph/9603133). Accurate fitting expressions for the relaxation time are obtained, and an efficient energy averaging procedure proposed. A Fortran code, which calculates the longitudinal transport properties of degenerate electrons in strong magnetic fields for any parameters of dense stellar matter of practical interest, is available from the authors upon request.