ABSTRACT

It is now feasible to design and build a high speed scanner system that can digitize astronomical images recorded on glass plates (8 x 10 in) to high photometric accuracy in under 30 sec. This makes possible the digital preservation of large volumes of archival data on plates which in turn enables time variability studies of many classes of astronomical objects to extend back a full century in time as never before possible. The longest duration set of astronomical plates, and with the largest amount of coverage, are contained in the 600,000 plates of the Harvard College Observatory. The cosmic "time machine" made possible by digitizing and serving a century of stellar data on high speed networks means that a number of key problems in astrophysics can be investigated. Three examples include: Long-term changes in the pulsation periods of Cepheid variable stars, the cosmic yardsticks of the astronomical distance scale, can be studied where period change measurements can reveal the poorly understood conditions of core convection in the interiors of these luminous stars; Stellar evolution can be observed on decade to century timescales in very young stars, which may be converting their left over material in surrounding disks into the birth of planets; In white dwarfs, neutron stars and black holes in binary systems, accreting matter from the binary companion, variability is the rule rather than the exception so they may be studied by the brightness changes, results of which point to the formation and evolution of these most extreme stars in the Galaxy. Not only can known phenomena and problems be addressed, but there is the very likely discovery of new and unexpected phenomena.

Broader Impacts. This research is helping to increase public awareness that the universe is not static. Evolution and change are the rule, not the exception. The impact on science education can be large: by showing on the project website segments of the ``cosmic movie" from quasar variations to Cepheid variable pulsation changes to nearby examples of change in newly-forming stars and planet systems, students can better understand the excitement of current astronomy. Physical understanding of the dynamic universe is even more enticing than the immutable sky.

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