Mapping the Night Sky

A number of digital sky surveys are creating a map of the night sky, so that by around 2020, astronomers will have catalogued almost all the galaxies, stars and asteroids that can be seen by ground-based telescopes, about 20 billion astronomical objects.

According to John Tonry of the University of Hawaii’s Institute for Astronomy in Honolulu, the situation mirrors that of past cartographers of the Earth. While Europeans knew almost nothing of the New World in the 13^th century, today they can find images of every place on Earth. 

The first of the sky surveys was the Sloan Digital Sky Survey, which began in 2000 at Apache Point Observatory in New Mexico. In its first five years of operation, it has snapped almost 20 million celestial objects in one fifth of the sky. 

Later surveys have been designed to map larger portions of the sky. Skymapper, which is being constructed at the Australian National University’s Siding Spring Observatory in New South Wales, and should begin observations in mid-2008, is supposed to map all of the sky south of the equator at visible wavelengths over five years. 

The Panoramic Survey Telescope and Rapid Response (Pan-STARRS), which began in August on the Hawaiian Island of Maui, will map about three quarters of they sky several times each month until 2010. Pan-STARRS 1, the first incarnation, uses the largest telescope in the world. Pan-STARRS 4, a follow-up survey will run from around 2010 to 2020 from a site on Mauna Kea. According to Brian Marsden, former director of the International Astronomical Union’s Minor Planet Center in Cambridge, Massachusetts, within 5 to 10 years, a million asteroids will be catalogued. The Pan-STARRS team is paying particular attention to asteroids that could collide with Earth.  It could also find previously unseen planets in the Solar System, and confirm or deny a hypothesis that the sun has a dwarf companion. 

From 2014 to 2024 the Large Synoptic Survey Telescope (LSST) should map three quarters of the whole sky in only three nights, if astronomers’ plans come to fruition. The LSST will operate from Cerro Pachon in northern Chile.