3,201 research outputs found
A Comparison of the Uses of Astrology in the Works of John Gower and Geoffrey Chaucer
The literary interest in astrology which had been gradually increasing during the fourteenth century in England, culminated in the works of Geoffrey Chaucer and John Gower. It is not surprising that these two poets have used astrology very extensively in writing stories for their medieval audiences since the average man in the Middles Ages believed that life depended upon the influences of the seven planets in their positions in the zodiac. It is the purpose of this thesis to present a comparison of the uses of the astrological material in the works of Geoffrey Chaucer and John Gower. In this comparison it will be necessary to divide this thesis into six parts in which passages from their works will be presented as evidence of the ways in which they have used astrology in writing for their medieval audience. It will be necessary to refer to some passages more than once. In the first part a comparison will be made of the personal beliefs of Chaucer and Gower concerning astrology. In the second part a comparison will be made of the ways in which these two poets have used astrological influences as motivating forces in their stories. In the third part a comparison will be made of the ways in which Chaucer and Gower have used astrological material in describing their characters and explaining their actions. It is the purpose of the fourth part to compare the powers and influences of the various planets as they are presented by Chaucer and Gower. In the fifth part a comparison will be made of the distinction in theory and practice between astrology and astronomy as they are presented in the works of Chaucer and Gower. In the sixth part, an effort will be made to determine whether or not Chaucer and Gower confused the seven planets with the ancient deities of the same name
Modeling Collisional Cascades In Debris Disks: Steep Dust-Size Distributions
We explore the evolution of the mass distribution of dust in
collision-dominated debris disks, using the collisional code introduced in our
previous paper. We analyze the equilibrium distribution and its dependence on
model parameters by evolving over 100 models to 10 Gyr. With our numerical
models, we confirm that systems reach collisional equilibrium with a mass
distribution that is steeper than the traditional solution by Dohnanyi (1969).
Our model yields a quasi steady-state slope of n(m) ~ m^{-1.88} [n(a) ~
a^{-3.65}] as a robust solution for a wide range of possible model parameters.
We also show that a simple power-law function can be an appropriate
approximation for the mass distribution of particles in certain regimes. The
steeper solution has observable effects in the submillimeter and millimeter
wavelength regimes of the electromagnetic spectrum. We assemble data for nine
debris disks that have been observed at these wavelengths and, using a
simplified absorption efficiency model, show that the predicted slope of the
particle mass distribution generates SEDs that are in agreement with the
observed ones.Comment: 12 pages, 10 figures, Accepted by ApJ, emulateap
Growth Response of Kenhy Fescue to Nitrogen Fertilizer
Kenhy fescue is a new, improved variety of tall fescue which has recently been released by the University of Kentucky Agricultural Experiment Station and the U.S.D.A. Agricultural Research Service (see University of Kentucky publication AGR-60, Kenhy A New Tall Fescue Variety ). Seed of this variety should become available to farmers in limited quantities in the summer 1977. The purpose of this report is to provide information on how this newly developed fescue variety produces as affected by time and rate of nitrogen application
Extinction and the Dimming of KIC 8462852
To test alternative hypotheses for the behavior of KIC 8462852, we obtained
measurements of the star over a wide wavelength range from the UV to the
mid-infrared from October 2015 through December 2016, using Swift, Spitzer and
at AstroLAB IRIS. The star faded in a manner similar to the long-term fading
seen in Kepler data about 1400 days previously. The dimming rate for the entire
period reported is 22.1 +\- 9.7 milli-mag/yr in the Swift wavebands, with
amounts of 21.0 +\- 4.5 mmag in the groundbased B measurements, 14.0 +\- 4.5
mmag in V, and 13.0 +\- 4.5 in R, and a rate of 5.0 +\- 1.2 mmag/yr averaged
over the two warm Spitzer bands. Although the dimming is small, it is seen at
>= 3 sigma by three different observatories operating from the UV to the IR.
The presence of long-term secular dimming means that previous SED models of the
star based on photometric measurements taken years apart may not be accurate.
We find that stellar models with T_{eff} = 7000 - 7100 K and A_V ~ 0.73 best
fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 microns, although a longer
wavelength excess from a substantial debris disk is still possible (e.g., as
around Fomalhaut). The wavelength dependence of the fading favors a relatively
neutral color (i.e., R_V >= 5, but not flat across all the bands) compared with
the extinction law for the general ISM (R_V = 3.1), suggesting that the dimming
arises from circumstellar material.Comment: accepted by the Astrophysical Journal; acknowledgements revised
9/1/201
Resolved Debris Discs Around A Stars in the Herschel DEBRIS Survey
The majority of debris discs discovered so far have only been detected
through infrared excess emission above stellar photospheres. While disc
properties can be inferred from unresolved photometry alone under various
assumptions for the physical properties of dust grains, there is a degeneracy
between disc radius and dust temperature that depends on the grain size
distribution and optical properties. By resolving the disc we can measure the
actual location of the dust. The launch of Herschel, with an angular resolution
superior to previous far-infrared telescopes, allows us to spatially resolve
more discs and locate the dust directly. Here we present the nine resolved
discs around A stars between 20 and 40 pc observed by the DEBRIS survey. We use
these data to investigate the disc radii by fitting narrow ring models to
images at 70, 100 and 160 {\mu}m and by fitting blackbodies to full spectral
energy distributions. We do this with the aim of finding an improved way of
estimating disc radii for unresolved systems. The ratio between the resolved
and blackbody radii varies between 1 and 2.5. This ratio is inversely
correlated with luminosity and any remaining discrepancies are most likely
explained by differences to the minimum size of grain in the size distribution
or differences in composition. We find that three of the systems are well fit
by a narrow ring, two systems are borderline cases and the other four likely
require wider or multiple rings to fully explain the observations, reflecting
the diversity of planetary systems.Comment: 19 pages, 13 figures, 6 tables. Accepted for publication in MNRA
Target Selection for the LBTI Exozodi Key Science Program
The Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS)
on the Large Binocular Telescope Interferometer will survey nearby stars for
faint emission arising from ~300 K dust (exozodiacal dust), and aims to
determine the exozodiacal dust luminosity function. HOSTS results will enable
planning for future space telescopes aimed at direct spectroscopy of habitable
zone terrestrial planets, as well as greater understanding of the evolution of
exozodiacal disks and planetary systems. We lay out here the considerations
that lead to the final HOSTS target list. Our target selection strategy
maximizes the ability of the survey to constrain the exozodi luminosity
function by selecting a combination of stars selected for suitability as
targets of future missions and as sensitive exozodi probes. With a survey of
approximately 50 stars, we show that HOSTS can enable an understanding of the
statistical distribution of warm dust around various types of stars and is
robust to the effects of varying levels of survey sensitivity induced by
weather conditions.Comment: accepted to ApJ
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