The first telescopic discovery of a double star is attributed to Giambattista Riccioli in 1650. It was of Mizar, the second star in the handle of Big Dipper asterism in Ursa Major. This was just 41 years after Galileo first turned his telescope to the heavens. Others stellar pairs were noted in the latter half of the 17th and early 18th centuries, by such noted astronomers as Huygens, Hooke, Bradey and Pound, but because there were viewed as mere curiosities and attributed to perspective, no effort was made to catalogue or study them.

It was not until late in the 18th century that serious attention was given them. A century after Galileo, William Herschel and Christian Mayer simultaneously published double star catalogues. So enthused by this new area of research, Herschel invited others to take up the study:

" I resolve to examine every star in the heavens with the utmost attention and a very high power, that I might collect such materials for this research as would enable me to fix my observations on those that would best answer my end. The subject has already proved so extensive, and still promises so rich a harvest to those who are inclined to be diligent in the pursuit, that I cannot help inviting every lover of astronomy to join with me in observations that must inevitably lead to new discoveries."

The "end" that Herschel sought was to measure stellar parallaxes by comparing the position of the primary star with that of its fainter neighbor (he assumed that the fainter star was much farther away along the same line of sight.) He reasoned that by observing the stellar pair at different times in the earth's orbit around the Sun, a shift in the relative positions of the two stars would be noted. However, as he accumulated data, Herschel came to recognize that the motions observed in these stellar systems were caused not by parallax but by orbital motion.

The accuracy of the study, conducted by William Herschel and later his son John, of binary systems was limited by the quality of the telescopes. Although they used reflectors of 18 ¾" and 48", they had mounts that were altazimuth and lacked any drives for tracking. Still they managed to amass double star catalogues containing more than 3000 pairs.

It was in 1824, two years after William Herschel's death, when the first tool, that would make a real difference in double star research, came into the hands of Friedrich George Wilhelm Struve at the Dorpat Observatory in Russia. That "tool" was the famous Fraunhofer 9" refractor equipped with equatorial mount, excellent driving mechanism and an accurate micrometer. With this instrument in hand Struve embarked on the first systematic survey of double stars and their measurements. After just 13 years of research he published the work "Mensurae Micrometricae" which included a catalogue of 3,314 pairs and detailed measurements of each. It was a monumental task that required Struve to observe up to 400 objects per hour! Later Otto Struve continued his father's work and added another 500 pairs.

For years following Struve's work astronomers seemed content to simply observe and measure the known pairs. During this time, many important measurements were recorded by such notables as Dawes, Smythe, Dembowski, Madler, Secchi, Bessel, Wilson and Gledhill.

However, it was not until 1873 that the work of discovering new pairs was taken up again by an American named Shelburne Wesley Burnham. Beginning as an amateur with a 130mm refractor and later as a professional with such telescopes as the 26" refractor at US Naval Observatory and the 40" refractor at the Yerkes observatory, Burnham was able to add more than 1300 new pairs; showing that earlier surveys were far from complete. Burnham's dilligent example spurred other to make great visual surveys. Starting in 1899 Robert Grant Aiken and William J. Hussey used the Lick Observatory's 36" refractor to survey the northern sky; yielding more than 4000 binaries in 16 years of work. Even after this survey was complete, in recent years, Paul Couteau, Wulff D. Heintz and Paul Muller re-surveyed the northern sky and located thousands of new pairs.

Still others have taken different approaches to add the the volume of known double stars. Edward C. Pickering and Hermann C. Vogel combined photography and steller spectroscopy in the late 1800's to include the discovery of spectroscopic binaries. In the 1930's, Gerald P. Kuiper, in his study of nearby stars, added an additional 117 pairs. And Charles Worley added nearly 30 more while studying M-dwarfs.

Each new research showed that prior work was not exhaustive. Telescope quality, atmospheric conditions and orbital period can all contribute to some pairs escaping the researcher's investigation. The result is that there are always unknown pairs or known pairs with erroneous measurements that can found by the diligent observer. In 1890, astronomy historian Agnes Clerk wrote" It is clear that a good deal of patience is needed for the investigation of double stars. The facts about them must often be allowed to ripen for a long time before they can be turned to account. Sooner or later, however their fruit cannot fail to appear. There is, perhaps, no other branch of science in which industry is so sure to be rewarded with definite results."

The work is not yet complete and sky awaits further inspection.

Questions or comments welcomed by P.J. Anway at: Email