60 research outputs found
Eta Carinae in the Context of the Most Massive Stars
Eta Car, with its historical outbursts, visible ejecta and massive, variable
winds, continues to challenge both observers and modelers. In just the past
five years over 100 papers have been published on this fascinating object. We
now know it to be a massive binary system with a 5.54-year period. In January
2009, Eta Car underwent one of its periodic low-states, associated with
periastron passage of the two massive stars. This event was monitored by an
intensive multi-wavelength campaign ranging from gamma-rays to radio. A large
amount of data was collected to test a number of evolving models including 3-D
models of the massive interacting winds. August 2009 was an excellent time for
observers and theorists to come together and review the accumulated studies, as
have occurred in four meetings since 1998 devoted to Eta Car. Indeed, Eta Car
behaved both predictably and unpredictably during this most recent periastron,
spurring timely discussions. Coincidently, WR140 also passed through periastron
in early 2009. It, too, is a intensively studied massive interacting binary.
Comparison of its properties, as well as the properties of other massive stars,
with those of Eta Car is very instructive. These well-known examples of evolved
massive binary systems provide many clues as to the fate of the most massive
stars. What are the effects of the interacting winds, of individual stellar
rotation, and of the circumstellar material on what we see as
hypernovae/supernovae? We hope to learn.Comment: 26 pages, 7 figures, IAU General Assembly Joint Discussion on Eta
Carinae in Context of the Most Massive Star
Origens da vida
We present a historical perspective about the ideas concerning the origin of life. After displaying the main topics necessary for understanding lifes origin, the main characteristics of the present life forms and their relationships are shown, suggesting a common ancestor. The conditions for prebiotic chemistry in terrestrial or interplanetary environments are reviewed. We put in context the arguments about the early origin of replicators versus metabolism. The very narrow window for life settlement in the early Earth is stressed, pointing to the likelihood of life arising in other places in the Universe. Finally, we present the cornerstones of current search for life outside our planet.Apresentamos um panorama geral das idéias sobre a origem da vida na história. Após delinearmos os principais temas necessários para o entendimento da origem da vida, mostramos as características básicas da vida atual e as relações entre os seres vivos que sugerem um ancestral comum. Revemos as condições químicas pré-bióticas no ambiente terrestre e fora dele. Quanto ao aparecimento da vida, confrontamos as principais vertentes sobre a precedência do código genético ou do metabolismo. Evidenciamos a curta janela de tempo para o estabelecimento da vida na Terra, indicando a facilidade de esse processo ocorrer no Universo. Finalmente, são apresentados os fundamentos dos projetos atuais de procura de vida fora de nosso planeta
Eta Carinae: Binarity Confirmed
We report the recovery of a spectroscopic event in eta Carinae in 1997/98
after a prediction by Damineli (1996). A true periodicity with P = 2020+-5 days
(0.2% uncertainty) is obtained. The line intensities and the radial-velocity
curve display a phase-locked behavior implying that the energy and dynamics of
the event repeat from cycle to cycle. This rules out S Doradus oscillation or
multiple shell ejection by an unstable star as the explanation of the
spectroscopic events. A colliding-wind binary scenario is supported by our
spectroscopic data and by X-ray observations. Although deviations from a simple
case exist around periastron, intensive monitoring during the next event (mid
2003) will be crucial to the understanding of the system.Comment: 13 pages, accepted by ApJ Letters (January 2000
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