‘All-sky’ surveys are a popular undertaking in astronomy these days. The 2MASS project is using telescopes in Arizona and Chile to photograph northern and southern skies in the 2-micrometre infrared range. The Digital Palomar Observatory Sky Survey is expected to catalogue some two billion sources in the north, and the Very Large Array in New Mexico has two sky surveys in progress.

These and other searches will generate tens of terabytes of high-quality astronomical images and data. The goal of the Digital Sky project is to show how all this information might be merged into a “multi-wavelength digital library covering a significant fraction of the real sky”.

Astrophysicist Tom Prince of the California Institute of Technology is the principal investigator, with funds coming from the US National Science Foundation's National Partnerships for Advanced Computational Infrastructure programme. Digital Sky will focus on the “switchyard” problem, says Prince — how to develop standards and techniques for merging data with different formats into a virtual, distributed database. The Sloan Digital Sky Survey, the most ambitious of the planned surveys, will not be incorporated in the Digital Sky database, but will be among the groups cooperating in setting the standards.

The payoff for future operational databases could be enormous. Scientists might, for example, be able to search easily a billion astronomical objects across a wide range of wavelengths, looking for unusual patterns of energy output.

Digital Sky is at http://www.cacr.caltech.edu/sda/digital_sky.html