NBC News Scripts
WBAP-TV (Television station : Fort Worth, Tex.)
1954-12-31
Search results
130 records were found.
The last twenty-five years have seen our understanding of the formation and abundance of planets revolutionised, thanks to the first detections of debris discs, and, a decade later, of the first extrasolar planets. Hardly a week now goes by without a planet discovery, and the range of methods used to search for planets has expanded to include techniques that are efficient at detecting different types of planets. By combining the discoveries of the various methods, we therefore have the opportunity to build a picture of planet populations across the Galaxy. In this thesis, I am presenting work done as a basis towards such an effort: first I present work carried out to improve modelling methods for gravitational microlensing events. Since the first microlensing observing campaigns, the amount of data of anomalous events has been increasi...
Gravitational Microlensing, as a technique for detecting Extrasolar Planets, is recognised for its potential in discovering small-mass planets similar to Earth, at a distance of a few Astronomical Units from their host stars. However, analysing the data from microlensing events (which statistically rarely reveal planets) is complex and requires continued and intensive use of various networks of telescopes working together in order to observe the phenomenon. As such the techniques are constantly being developed and refined; this project outlines some steps of the careful analysis required to model an event and ensure the best quality data is used in the fitting. A quantitative investigation into increasing the quality of the original photometric data available from any microlensing event demonstrates that 'lucky imaging' can lead to a m...
The transit method is considered to be one of the most promising for discovering extrasolar planets.
However, the method requires photometric precision of better than
∼
1%. If we are able to
achieve this kind of accuracy, then we are set to discover extrasolar planets. The uniqueness of my
experiment will lead to the discovery of transiting planets around the brightest and most important
stars quicker than the competitors in the field. The importance of the transit method stems from
being able to supply many more planetary parameters than other methods, which plays a crucial
role in testing planet formation theories. This thesis is divided into eight chapters.
The first chapter provides a general background about transits and their theory. We discuss
other methods of extrasolar planet detection, recent developments, future sp...
This thesis presents a study of the sub-light year regions of Active Galactic Nuclei (AGN). These environments contain accretion discs that orbit a central super-massive black hole. The luminosity of the AGN inner regions varies over time across all wavelengths with variability at longer wavelengths lagging behind that at shorter wavelengths. Since the AGN themselves are too remote and too compact to resolve directly, I exploit these time lags to infer the physical characteristics of the accretion disc and surrounding gas clouds that emit broad emission lines. These characteristics include the inclination and temperature profile of the accretion disc, and the shape (or light curve) of the luminosity fluctuations that drive the accretion disc variability.
This thesis details the work in the first author papers of Starkey et al. (2016...
In this thesis I study the inner-most regions of Active Galactic Nuclei (AGN) using
the reverberation mapping technique, and neutron star low-mass X-ray binaries in
quiescence using X-ray observations.
Using the 13-year optical monitoring data for the AGN NGC 5548, the luminosity dependence
of the Hβ emitting radius was modelled using a delay map, finding that
the radius scales with luminosity as predicted by recent theoretical models. Time-delays
between the continuum at different wavelengths in AGN can be used to probe the accretion
disc. Here, continuum time-delays in a sample of 14 AGN were used to measure the radial
temperature profile of the accretion discs, determine the nuclear extinction, and measure
distances to the objects. However, the distances measured correspond to a value for
Hubble's constant that is a factor...
M.Tech. (Human Resources Development)
Static, spherically-symmetric particle-like solutions to the coupled Einstein-Dirac and Einstein-Dirac-Maxwell equations have been studied by Finster, Smoller and Yau (FSY). In their work, FSY left the fermion mass as a parameter set to ±1. This thesis generalises these equations to include the Higgs field, letting the fermion mass become a function through coupling, μ. We discuss the dynamics associated with the Higgs field and find that there exist qualitatively similar solutions to those found by FSY, with well behaved, non-divergent metric components and electrostatic potential, close to the origin, going over to the point-particle solutions for large r; the Schwarzschild or Reissner-Nordström metric, and the Coulomb potential. We then go on to discuss an alternative gravity theory, conformal gravity, (CG), and look for solutions o...
Gravitational microlensing is a well established and unique field of time-domain astrophysics. For two decades microlensing surveys have been regularly observing millions of stars to detect elusive events that follow a characteristic Paczyński lightcurve. This workshop reviewed the current state of the field, and covered the major topics related to microlensing: searches for extrasolar planets, and studies of dark matter. There were also discussions of issues relating to the organisation of follow-up observations for microlensing, as well as serendipitous scientific outcomes resulting from extensive microlensing data.
