  Astronomy is entering a new era of discovery, coincident with the
establishment of new facilities for observation and simulation that will
routinely generate petabytes of data. While an increasing reliance on automated
data analysis is anticipated, a critical role will remain for
visualization-based knowledge discovery. We have investigated scientific
visualization applications in astronomy through an examination of the
literature published during the last two decades. We identify the two most
active fields for progress - visualization of large-N particle data and
spectral data cubes - discuss open areas of research, and introduce a mapping
between astronomical sources of data and data representations used in general
purpose visualization tools. We discuss contributions using high performance
computing architectures (e.g: distributed processing and GPUs), collaborative
astronomy visualization, the use of workflow systems to store metadata about
visualization parameters, and the use of advanced interaction devices. We
examine a number of issues that may be limiting the spread of scientific
visualization research in astronomy and identify six grand challenges for
scientific visualization research in the Petascale Astronomy Era.
