A new way to study the sky is called “wide-field sky survey”. Instead of looking at individual objects, the surveys take an inventory of everything that meets certain criteria in a large region of the sky.

The Sloan Digital Sky Survey (SDSS) images and measures hundreds of millions of stars, galaxies, and quasars. The Two Micron All Sky Survey (2MASS) imaged the entire sky at high resolution in three infrared colors. The Two-Degree Field (2dF) survey measured the redshifts of more than a quarter million galaxies and quasars.

The AAO/UKST Hydrogen-alpha Survey is a four-year project at the Anglo-Australian Observatory using the 1.24 meter U.K. Schmidt Telescope. It has surveyed the southern Milky Way and the Magellanic Clouds through the world’s largest astronomical H-alpha filter to highlight dim nebulae. Scans of the photographs have already turned up about 1,000 new planetary nebulae. A planetary nebula is a thin shell of gas blown off from and illuminated by a very hot star. The gas expands at a very high speed as it spreads and disperses into the interstellar medium of space. Before this study, only about 1,000 were known to exist.

Some of the planetary nebulae are large, dim, and highly evolved, others are close pairs, new sets of shells and outer structures around previously known nebulae. Several hundred planetary nebulae were discovered in the galaxy’s central bulge. These nebulae will be studied as tracers for bulge dynamics because their strong emission lines allow astronomers to measure their radial velocities (speeds) accurately.

The survey also shows rich detail in many other, wider-field hydrogen structures that are slowly spreading out and disappearing into the Milky Way.