Overview: Our basic research goal is to observe and study the internal structure and composition of white dwarf stars, the remnants of a nuclear fusion furnace that once turned hydrogen into helium and energy, a process which still powers stars like the Sun. An unexpected circumstance allows us to probe their structure: some of these stars vibrate in a periodic manner that sends seismic waves deep through their interior and brings information to the surface. We see this manifested as complex periodic variations in their brightness, which we can study and analyze, much as seismologists study the inner structure of the earth using earthquakes. White dwarfs once supported steady nuclear fusion, and would again if hydrogen were injected into them. We essentially have a working fusion laboratory to study, one that we must understand in detail if we are ever to master this clean sustainable energy source and duplicate the process on this planet.Whole Earth TelescopeWe can determine the internal structure of pulsating white dwarfs using the techniques of high speed photometry to observe their variations in brightness over time, and then matching these observations with a computer model which behaves the same way. The parameters of the model are chosen to correspond one-to-one with the physical processes that give rise to the variations, so a good fit to the data gives us confidence that our model reflects the actual physics of the stars themselves. In the past decade, the observational requirements of white dwarf seismology have been satisfied by the development of the Whole Earth Telescope an informal collaboration of astronomers at observatories around the globe who cooperate to produce nearly continuous time-series photometry of white dwarfs for up to 14 days at a time. This instrument has provided a wealth of seismological data on the different varieties of pulsating white dwarf stars.In an effort to bring the analysis of WET data to the level of sophistication demanded by the observations, we are developing a model-fitting method based on a genetic algorithm. The underlying ideas for genetic algorithms were inspired by Charles Darwin's notion of biological evolution through natural selection. The basic idea is to solve a problem by evolving the best solution from an initial set of random guesses. The computer model provides the framework within which the evolution takes place, and the individual parameters controlling it serve as the genetic building blocks. Observations provide the selection pressure. In practice, this method is much more efficient than other comparably global techniques.
Time-series CCD photometer:The study of pulsating white dwarfs requires a special kind of instrument capable of high speed imaging. When studying phenomena that change rapidly, we do not have the luxury of increasing our exposure time to improve the signal. Our instrument must be highly efficient even with short exposures. We also need high timing precision to determine the beginning and duration of each exposure accurately. Most CCD cameras cannot obtain data continuously -- there is a dead time between exposures when the detector is busy reading out the previous image. The time required varies from a few seconds to a few minutes. We need an instrument with essentially zero dead time, so we can record the rapidly variable phenomena without interruption.We are a tax-exempt non-profit organization dedicated to scientific research and public education. We support and conduct scientific research on topics relevant to the observational and theoretical properties of stars, and we create and distribute public education resources through our website. If you would like to support one of the projects below by donating equipment, time, or funding, please find out how you can help or consider making a secure online donation. If you have any questions, or other ideas for how you might be able to gete public education of stars, involved with one of these projects.
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