by Case » Tue Nov 21, 2017 12:29 pm
APOD Robot wrote:… constellation designated by the International Astronomical Union in 1922 …
Celestial nomenclature had long been a controversial topic. At its inaugural meeting in May 1922 in Rome, the IAU
standardized the constellation names and three-letter abbreviations. (So, for instance, Ursa Major is abbreviated to UMa.) Ejnar Hertzsprung had
suggested (and personally used for years) two-letter abbreviations and Henry Norris Russell
had compiled an alternative list of three-letter abbreviations. (Yes, the same guys that made the
famous diagram.)
Originally the constellations were defined informally by the shapes made by their star patterns, but, as the pace of celestial discoveries quickened in the early 20th century,
astronomers decided it would be helpful to have an official set of constellation boundaries. One reason was to aid in the naming of new variable stars, which are named for the constellation in which they reside, so it is important to agree where one constellation ends and the next begins. Eugène Delporte originally listed the 88 “modern” constellations on behalf of the IAU Commission 3 (Astronomical Notations), in
Délimitation scientifique des constellations (Delporte, 1930). (
He expanded on Benjamin Gould’s boundaries for the southern constellations.)
Delporte drew the boundaries along vertical and horizontal lines of right ascension and declination; however, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (e.g., for epoch J2000) are already
somewhat skewed and no longer perfectly vertical or horizontal.
[float=left][img]https://i.imgur.com/HfNdGG7.png[/img][/float][quote="APOD Robot"]… constellation designated by the International Astronomical Union in 1922 …[/quote]
Celestial nomenclature had long been a controversial topic. At its inaugural meeting in May 1922 in Rome, the IAU [url=https://www.iau.org/public/themes/naming/]standardized[/url] the constellation names and three-letter abbreviations. (So, for instance, Ursa Major is abbreviated to UMa.) Ejnar Hertzsprung had [url=http://www.ianridpath.com/hertzsprungabbrs.htm]suggested[/url] (and personally used for years) two-letter abbreviations and Henry Norris Russell [url=http://www.ianridpath.com/iaulist1.htm]had compiled[/url] an alternative list of three-letter abbreviations. (Yes, the same guys that made the [url=https://en.wikipedia.org/wiki/Hertzsprung-Russell_diagram]famous diagram[/url].)
Originally the constellations were defined informally by the shapes made by their star patterns, but, as the pace of celestial discoveries quickened in the early 20th century, [url=https://www.iau.org/public/themes/constellations/]astronomers decided[/url] it would be helpful to have an official set of constellation boundaries. One reason was to aid in the naming of new variable stars, which are named for the constellation in which they reside, so it is important to agree where one constellation ends and the next begins. Eugène Delporte originally listed the 88 “modern” constellations on behalf of the IAU Commission 3 (Astronomical Notations), in [i]Délimitation scientifique des constellations[/i] (Delporte, 1930). ([url=http://calgary.rasc.ca/constellation.htm#history]He expanded[/url] on Benjamin Gould’s boundaries for the southern constellations.)
Delporte drew the boundaries along vertical and horizontal lines of right ascension and declination; however, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (e.g., for epoch J2000) are already [url=https://en.wikipedia.org/wiki/88_modern_constellations_by_area]somewhat skewed[/url] and no longer perfectly vertical or horizontal.