Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt.........8c&link_type=abstract
Thesis (PH.D.)--THE UNIVERSITY OF TEXAS AT AUSTIN, 1995.Source: Dissertation Abstracts International, Volume: 56-06, Section: B,
Other
19
Scientific paper
The age of our own Galaxy--the Milky Way--is one of the principal pieces of information we have to constrain our understanding of how the Universe evolved to its current state. With the assumption that our Galaxy is no different than any other of its type and that our locale in the Universe in not unique, the age of the Milky Way places constraints on how much time has elapsed since galaxies and the Universe were first formed. Estimates for the Galaxy's age have ranged from 10 to 20 billion years, but this age spread is too large to constrain the models we have describing the evolution of the Universe. Perhaps the most accurate way we have of estimating ages comes from the white dwarf stars--the cooling remnants of stellar evolution. The difficulty is that there are too few white dwarfs known for us to fully exploit them as the accurate chronometers they are. In the first part of this work I present new instrumentation and photometric techniques designed specifically to search for and identify the oldest white dwarf stars. In collaboration with Phillip MacQueen I have converted the 0.76m Boller and Chivens telescope at McDonald Observatory into a highly sensitive digital f/3 Prime Focus Camera. I have also extended the standard UBVRI photometry system to isolate the unique color signatures of cool degenerate white dwarf stars. Using these new tools I have surveyed 2.1 square degrees around the Praesepe star cluster and identified its white dwarfs, which I have used to estimate its age at 1.0 +/- 0.3 billion years. From the same data set I have simultaneously obtained an age of 0.85 +/- 0.10 billion years for the cluster from main sequence stellar isochrones. I have also used the preliminary data from the Hipparcos mission to estimate an isochrone age for the Galactic Disk of 15 +/- 2.5 billion years. From these results I present a calibration of stellar isochrone ages to white dwarf cooling times and conclude that the Milky Way is 11 +/- 2 billion years old. Finally I use my estimated age of the Milky Way to place a value on the age of the Universe: 12 +/- 2 billion years.
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