Highly He-rich Matter Dredged Up by Extra Mixing through Stellar Encounters in Globular Clusters Suda et al. Wed, 14 Nov 2007 00:00:00 -0600 The unveiled main-sequence splitting in ω Centauri as well as NGC 2808 suggests that matter highly enriched in He (in terms of its mass fraction [FORMULA]) was produced and made the color of some main-sequence stars bluer in these globular clusters (GCs). The potential production site for the He-rich matter is generally considered to be massive AGB stars that experience the second dredge-up. However, it is found that massive AGB stars provide the matter with [FORMULA] at most, while the observed blueshift requires the presence of [FORMULA] matter. Here we show that extra mixing, which operates in the red giant phase of stars less massive than ∼2 M, could be a mechanism that enhances He content in their envelopes up to [FORMULA]. The extra mixing is supposed to be induced by red giant encounters with other stars in a collisional system like GCs. The [FORMULA] matter released in the AGB phase has alternative fates of (1) escaping from a GC or (2) being captured by kinematically cool stars through encounters. The AGB ejecta in ω Cen, which follows the latter case, can supply sufficient He to cause the observed blueshift. Simultaneously, this scheme generates the extreme horizontal branch, as observed in ω Cen, in response to the higher mass-loss rates, which is also caused by stellar encounters. Silicate Dust in the Environment of RS Ophiuchi following the 2006 Eruption Evans et al. Wed, 14 Nov 2007 00:00:00 -0600 We present further Spitzer Space Telescope observations of the recurrent nova RS Ophiuchi, obtained over the period 208–430 days after the 2006 eruption. The later Spitzer IRS data show that the line emission and free-free continuum emission reported earlier is declining, revealing incontrovertible evidence for the presence of silicate emission features at 9.7 and 18 μm. We conclude that the silicate dust survives the hard radiation impulse and shock blast wave from the eruption. The existence of the extant dust may have significant implications for understanding the propagation of shocks through the red giant wind and likely wind geometry. The Dependence of Galaxy Luminosity on Environment in a Volume-limited Sample of the Main Galaxy Sample of SDSS DR6 Deng, He, and Jiang Wed, 14 Nov 2007 00:00:00 -0600 From the volume-limited main galaxy sample of SDSS DR6, we extracted isolated galaxies and identified groups by different algorithms, in order to investigate the dependence of galaxy luminosity on environment. We compared the luminosity distributions of member galaxies of groups with that of isolated galaxies and the volume-limited main galaxy sample, and found that the luminosity distributions of member galaxies of groups are almost the same as that of the volume-limited sample, but are different from that of isolated galaxies: isolated galaxies have a higher proportion of faint galaxies ([FORMULA]) and a lower proportion of luminous galaxies ([FORMULA]) than member galaxies of groups. The level of significance is at least 3 σ. This shows that luminous galaxies exist preferentially in the densest regions of the universe (e.g., in groups), but faint galaxies are located preferentially in low-density regions. We also note that the dependence of galaxy luminosity on dense environment (e.g., in groups) is much weaker than that on underdense environment (e.g., isolated galaxies).
ADAF Theory - Accretion disk theory, mixing-length theory of convection, advection-dominated accretion flows.
404AMASE - Astrophysics Multi-spectral Archive Search Engine - An online astrophysics catalog developed using object-oriented database technology to help researchers locate multi-mission data in the NASA archives.
Meta Description: [ Web Site for the AMASE Multispectral Archive Search Engine ]
404Astrophysical Data - A nice beginners collection of constants and other data, assorted in one page... Beginner level, with links to more advanced sites.
Astrophysics - E-Print archive since April of 1992.
Astrophysics and Astronomy - Introductory essays on astrophysics and astronomy.
Meta Description: [ An intruduction into astronomy and astrophysics ]
Cambridge Relativity - Beginner's guide to all the basic concepts of Astrophysics written by active scientists at Cambridge University, UK.
404Contents - Accretion in astrophysics - active galactic nuclei, processes and dynamics.
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Encyclopedia of Astronomy and Astrophysics - Comprehensive archive of explantory articles on all key Astrophysics topics, categorised and fully searchable; actively updated by the Institute of Physics.
Fermilab Theoretical Astrophysics Group - Partially funded by a NASA Astrophysics Theory grant, find information about the group's past and future meetings.
Gravity is Cool, or, Why our Universe is Hospitable to Life - Text of the 1999 Oppenheimer lecture at UC Berkeley given by professor Freeman Dyson on the origin of life and other subjects.
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Modified Newtonian Dynamics - Overview of a controversial theory which is not generally accepted by the astrophysical community.
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Red Shift by Photon Decay - Author explains how Hubble's red shift of starlight spectra results from photon decay, proportional to traveled distance.
Meta Description: [ Photon Decay describes observed Hubble Red Shift by Maxwell equations
with first order diffusion term, and conserves speed of light c and action quantum h. ]
SIMBAD Astronomical Database - The SIMBAD astronomical database provides basic data, cross-identifications and bibliography for astronomical objects outside the solar system. SIMBAD can be queried by object name, coordinates, other criteria (filters), and lists of objects.
404Smithsonian Astrophysical Observatory - A research institute of the Smithsonian Institution headquartered in Cambridge, MA, where it is joined with the Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center for Astrophysics (CfA).
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Solar System - Celestial Mechanics - Presents ideas about the rotation of the sun and planets.
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Temporal Annex - Information mostly on the fourth dimension and theoretical physics.
The Astrophysical Journal - Devoted to recent developments, discoveries, and theories in astronomy and astrophysics.
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The Astrophysics Spectator - Articles published on this site cover current research in astronomy and astrophysics, describe our current understanding of astronomical phenomena, and comment on issues related to astronomical research.
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The Electric Universe - Physics knows four forces; 20th-century scientists were convinced that one of those, the electric force, played no macroscopic role in the Universe; site explains why that is incorrect.
Meta Description: [ Physics knows four forces. However, the 20 th century was convinced that one of the them the electric force plays no macroscopic role in the Universe. For example, positively charged atoms exist, but positively charged stars should not exist. ]
The NASA Astrophysics Data System - The Astrophysics Data System (ADS) is a NASA-funded project which maintains four bibliographic databases containing more than 4.0 million records: Astronomy and Astrophysics, Instrumentation, Physics and Geophysics, and preprints in Astronomy.
The Structure, Stability, and Dynamics of Self-Gravitating Systems - An interactive Astrophysics textbook from Louisiana State University.
Meta Description: [ The Structure, Stability, and Dynamics of Self-Gravitating Systems, an on-line, interactive, graduate-level Astrophysics textbook by Joel E. Tohline. ]
The Titius-Bode Number Sequence Deciphered - An explanation of the Titius-Bode Law of planetary spacing.
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THIS-Tuneable Heterodyne Infrared Spectrometer - THIS - instrument pages for the Tuneable Heterodyne Infrared Spectrometer developed by the University of Cologne. THIS is a transportable receiver designed for atmospheric and astrophysical observations in the mid infrared spectral region (7-28 µm).
Titius-Bode Law - Overview of the Titius-Bode Law.
Meta Description: [ Titius-Bode Law: Jupiter ]
404WCRI WalkerScience - Examines several aspects of astrophysics including the big bang, origin of heavy elements and satellites, dark matter and dark energy.
You Be the Astrophysicist - Interactive site for learning about astronomy and astrophysics.
Meta Description: [ Science is a process of inquiry. Scientists propose hypotheses and test them with experiments. In these pages you will begin with several options for experiments that may lead to the answer you are seeking., This site is intended for students age 14 and up, and for anyone interested in learning a... ]
