STAR CHARTS AND CATALOGUES
Who made the first star chart or catalogue? There is little doubt that
Eudoxus (B. C. 200) was the first to set down the positions of all the
brighter stars on a celestial globe, and he did this from observations
with a gnomon and an armillary sphere. Later Hipparchus (B. C. 130)
constructed the first known catalogue of stars, so that astronomers of a
later day might discover what changes are in progress among the stars,
either in their relative positions or caused by old stars disappearing
or new stars appearing at times in the heavens. Hipparchus was an
accurate observer, and he discovered an apparent and perpetual shifting
of the vernal equinox westward, by which the right ascensions of the
stars are all the time increasing. He determined the amount of it pretty
accurately, too. His catalogue contained 1,080 stars, and is printed in
the "Almagest" of Ptolemy.
Centuries elapsed before a second star catalogue was made, by Ulugh-Beg,
an Arabian astronomer, A. D. 1420, who was a son of Tamerlane, the
Tartar monarch of Samarcand, where the observations for the catalogue
were made. The stars were mainly those of Ptolemy, and much the same
stars were reobserved by Tycho Brahe (A. D. 1580) with his greatly
improved instruments, thus forming the third and last star catalogue of
importance before the invention of the telescope.
From the end of the seventeenth century onward, the application of the
telescope to all the types of instruments for making observations of
star places has increased the accuracy many-fold. The entire heavens has
been covered by Argelander in the northern hemisphere, and Gould in the
southern--over 700,000 stars in all. Many government observatories are
still at work cataloguing the stars. The Carnegie Institution of
Washington maintains a department of astrometry under Boss of Albany,
which has already issued a preliminary catalogue of more than 6,000
stars, and has a great general catalogue in progress, together with
investigations of stellar motions and parallaxes. This catalogue of star
positions will include proper motions of stars to the seventh magnitude.
In 1887 on proposal of the late Sir David Gill, an international
congress of astronomers met at Paris and arranged for the construction
of a photographic chart of the entire heavens, allotting the work to
eighteen observatories, equipped with photographic telescopes
essentially alike. The total number of plates exceeds 25,000. Stars of
the fourteenth magnitude are recorded, but only those including the
eleventh magnitude will be catalogued, perhaps 2,000,000 in all. The
expense of this comprehensive map of the stars has already exceeded
$2,000,000, and the work is now nearly complete. Turner of Oxford has
conducted many special investigations that have greatly enhanced the
progress of this international enterprise.
Other great photographic star charts have been carried through by the
Harvard Observatory, with the annex at Arequipa, Peru, employing the
Bruce photographic telescope, a doublet with 24-inch lenses; also
Kapteyn of Groningen has catalogued about 300,000 stars on plates taken
at Cape Town. Charting and cataloguing the stars, both visually and
photographically, is a work that will never be entirely finished.
Improvements in processes will be such that it can be better done in the
future than it is now, and the detection of changes in the fainter stars
and investigation of their motions will necessitate repetition of the
entire work from century to century.
The origin of the names of individual stars is a question of much
interest. The constellation figures form the basis of the method, and
the earliest names were given according to location in the especial
figure; as for instance, Cor Scorpii, the heart of the Scorpion, later
known as Antares or Alpha Scorpii. The Arabians adopted many star names
from the Greeks, and gave about a hundred special names to other stars.
Some of these are in common use to-day, by navigators, observers of
meteors and of variable stars. Sirius, Vega, Arcturus, and a few other
first magnitude stars, are instances.
But this method is quite insufficient for the fainter stars whose
numbers increase so rapidly. Bayer, a contemporary of Galileo,
originated our present system, which also employs the names of the
constellations, the Latin genitive in each case, prefixed by the small
letters of the Greek alphabet, from alpha to omega, in order of
decreasing brightness; and followed by the Roman letters when the Greek
alphabet is exhausted.
If there were still stars left in a constellation unnamed, numbers were
used, first by Flamsteed, Astronomer Royal; and numbers in the order of
right ascension in various catalogues are used to designate hundreds of
other stars. The vast bulk of the stars are, however, nameless; but
about one million are identifiable by their positions (right ascension
and declination) on the celestial sphere.