Surveying the Universe With Increased Accuracy
Astronomers and engineers carefully design giant visible-light and infrared telescopes, including the NGST and the GSMT, to make detailed observations of the individual objects they have found, such as galaxies, quasars, or protoplanetary disks. In addition, however, we also require telescopes capable of surveying the entire sky, providing us with the numbers and distribution of different species of cosmic objects. Astronomy has continually benefited from such surveys, each of them made with greater accuracy than its predecessors, probing deeper into space by recording objects still fainter than previous surveys could within a particular domain of the spectrum. These survey efforts might seem relatively straightforward exercises in improving our catalogs of the cosmic zoo, but each significant improvement in survey techniques has opened the door to new discoveries, and often to entire new realms of astronomical objects.
In addition to future discoveries, which we cannot predict with specificity, surveys offer the opportunity to resolve long-standing astronomical mysteries. One such mystery deals with the recent discovery that the universe teems with dark energy, energy that lurks in empty space and accelerates the universe’s expansion. Surveys of galaxies can test this discovery by determining whether the observed distribution of galaxies matches the prediction of a model in which the universal expansion indeed has entered an accelerating phase.
Until now, surveys of the cosmos have proceeded, by necessity, on the supposition that the universe remains the same on time scales measured in a few years, the time needed to complete a single survey. This supposition has governed surveys of galaxies, stars, or asteroids (the small objects that orbit our Sun by the hundreds of thousands). During the next decade, it will become possible to make a complete survey of the sky a hundred times more rapidly than before. Such a survey will add the time dimension to the three dimensions of space, revealing objects that vary on time scales measured in days. Thus, for example, the new surveys will reveal a host of exploding stars, which typically remain visible only for a few weeks or months. The new survey techniques will replace still photographs of the cosmos with an ongoing movie — a movie that will show more detail in each frame than any of the still frames of its predecessors.
Read More About The Large-Aperture Synoptic Survey Telescope (LSST)