June 4, 2001
Photo No: H2001-18b (top right image)
Bigger, Better Catalog Unveils Half a Billion Celestial Objects
These frames are samples from the photographic sky surveys,
which have been digitized by a technical team at the Space Telescope
Science Institute to support the Hubble Space Telescope operations.
The team processed these images to create a new astronomical
catalog, called the Guide Star Catalog II. This project was undertaken
by the Space Telescope Science Institute as an upgrade to an earlier
sky survey and catalog (DSS-I and GSC-I), initially done to provide
guide stars for pointing the Hubble Space Telescope. By virtue of its
sheer size, the DSS-II and GSC-II have many research applications
for both professional and amateur astronomers.
An example from the DSS-II shows the Rosette Nebula,
(originally photographed by the Palomar Observatory) as
digitized in the DSS-I (left) and DSS-II (right). The DSS-II
includes views of the sky at both red and blue wavelengths,
providing invaluable color information on about one billion
This blow-up of the inset box in the raw DSS-I scan shows
examples of the GSC-I and the improved GSC-II catalogs.
Astronomers extracted the stars from the scanned plate of
the Rosette and listed them in the catalogs. The new GSC-II
catalog provides the colors, positions, and luminosities of
nearly half a billion stars -- over 20 times as many as the
original GSC-I. The GSC-II contains information on stars as
dim as the 19th magnitude.
Credit: NASA, the DSS-II and GSC-II Consortia (with
images from the Palomar Observatory-STScI Digital Sky
Survey of the northern sky, based on scans of the Second
Palomar Sky Survey are copyright © 1993-1999 by the
California Institute of Technology)