In recent years, a number of services have arisen to offer people the opportunity to name a star after themselves or someone they care about. While these services allow those who use them to honor a loved one or stroke their own egos, they do not carry weight in the astronomical community. The methods for naming a star have changed over the centuries and are presently governed by the International Astronomical Union (IAU). Some stars have proper names, others are named for how bright they are, and other stars are named for their positions within their constellation. Following is an explanation of how star names are determined.
Giving Stars Proper Names
1Give a star a proper name according to its mythological significance. Just as many constellations are associated with myths or legends, the stars within them were given their names for the myths they were associated with.
- The constellation Gemini represents the twin sons of Queen Leda of Sparta who could not be separated by the death of 1 of them. The names of the 2 brightest stars in that constellation, Castor and Pollux, were the twins' names.
- The 7 brightest stars of the Pleiades represented and are named for the 7 daughters of Atlas and Pleione pursued by Orion: Alcyone, Celaeno, Electra, Maia, Merope, Sterope, and Taygeta.
- The proper name of the brightest star in the constellation Canis Major, Sirius, means "searing" or "scorching." This name derives from the ancient Egyptians' belief that when Sirius rose with the sun in early August, it added its heat to the sun's. (Sirius' nickname, the "Dog Star," is the origin of the phrase "dog days of summer" for this time period.)
- A star's proper name may derive from a different myth than that of the constellation it is in. The star Alkaid was seen as the leader of a funeral procession and so named by the Egyptians, but the constellation it is found in, Ursa Major, was seen as a bear by the Greeks.
2Give a star a proper name according to its position in the sky or constellation. Many stars' proper names derive from their position within their own constellation or a neighboring constellation.
- The bright star Deneb in the constellation Cygnus comes from the Arabic for "tail," as it represents the swan's tail. Likewise, the star Denebola in Leo represents the lion's tail, and the star Deneb Kaitos in Cetus represents the whale's tail.
- �Betelgeuse" means "armpit" and "Rigel" means "foot" in Arabic; the stars Betelgeuse and Rigel are the right armpit and left foot, respectively, of the constellation Orion.
- The name of the star Arcturus in the constellation Bootes means "bear driver'; it follows the constellations Ursa Major and Ursa Minor as they orbit the Celestial North Pole.
3Give a star a proper name for its astronomical properties. Some proper star names derive from properties astronomers were able to observe, either with the naked eye or crude lenses.
- The star Algol in Perseus takes its name from the Arabic "al ghul," meaning "ghoul" or "demon." The star is an eclipsing binary that appears dimmer when the dimmer star is closer to Earth than the brighter star. (The star represents the head of Medusa, the Gorgon slain by Perseus.)
- The star Mira in Cetus takes its name from the Latin word meaning "wonderful" (the same root as "miracle"). It is a variable star that changes in brightness over a regular period of time.
4Give a star a proper name for other reasons. While modern star registries allow people to give unofficial names to stars to honor themselves or their loved ones, a few official proper star names were given for similar reasons. The star Cor Caroli in the constellation Canes Venatici was named in honor of Great Britain's King Charles II; its name means "Charles' Heart."
Other Methods for Naming Stars
1Name a star for its brightness within its constellation. Around 1600, German astronomer Johannes Bayer developed the first modern system for naming stars based on their apparent brightness within their constellation. He used Greek letters to rank stars from brightest to dimmest ("Alpha" being brightest and "Omega" being dimmest), followed by upper and lowercase Roman letters when he ran out of Greek letters. A star's name was composed of its brightness rank and the possessive form of its name, thus the brightest star in the constellation Centaurus was designated Alpha Centauri under Bayer's system.
- Bayer's system did not always name stars purely by their brightness; sometimes he also took the position of the star within its constellation into account. Bayer designated Castor as "Alpha Geminorum" and Pollux as "Beta Geminorum," even though Pollux is actually brighter than Castor, because Castor appears above and to the right of Pollux in the sky.
- Bayer's method was later modified by adding letters after star names to indicate individual stars within a multiple star system, such as Alpha Centauri A and Alpha Centauri B, and numbers after the magnitude designator, as in Pi-1 Orionis, Pi-2 Orionis, and so on.
2Name a star for its position within its constellation. Developed by John Flamsteed in the 18th century, the Flamsteed method numbered the westernmost star within a constellation as "1," the next westernmost as "2," and so on, using the possessive name as a suffix. The westernmost star in Leo would thus be designated 1-Leonis in the Flamsteed system.
- The Bayer and Flamsteed naming conventions are often used in conjunction with proper star names. If a star has a proper name, it is generally known by that; if not, by its Bayer name; if it has neither a proper name or a Bayer name, then by its Flamsteed number. The main exception to this rule is Alpha Centauri, which is known by its Bayer name instead of its proper name of Toliman (and by aviators and mariners as Rigil Kentaurus).
3Name a star according to its right ascension and declination, without regard to its constellation. Because the system of proper names, Bayer names, and Flamsteed numbers favors brighter stars and ignores the larger number of dimmer stars, a different method was necessary to catalog all the stars in the night sky. This method involves cataloging a star by its right ascension, its distance from the vernal equinox, and its declination from the Celestial Equator. Such catalogs often break the sky into strips of either right ascension (celestial longitude) or declination (celestial latitude) and enumerate stars within these strips.
- The Harvard Revised Bright Star Catalogue (now compiled at Yale University) lists 9000 stars down to 6th magnitude from west to east. The star Vega in the constellation Lyra is known as HR 7001 in this catalogue.
- The 19th century Bonner Durchmusterung (Bonn Survey) covered stars visible in the northern sky down to 10th magnitude, dividing each degree of declination into its strip. In this catalog, Vega would be designated BD38 3238. (A companion survey, the Cordoba Durchmusterung, covered the southern sky.)
- The most commonly used star catalog today is the Henry Draper catalog, which numbers its stars solely by right ascension. In it, Vega is designated HD 172167. Other star catalogs include the Smithsonian Astrophysical Observation and the Hipparcos International Catalogue; Vega is designated as SAO 067174 and HIC 91262 in these catalogs, respectively.
- Some stars may have more than 1 proper name given to them. The star Alkaid in Ursa Major is also known as Benetnasch; the star Alpheratz in Andromeda is also known as Sirrah. Which name is the preferred proper name is determined by the International Astronomical Union.
- Star catalogs based on the stars' positions in the sky are subject to periodic revision because of the precession of Earth's axes and the proper motion of the stars with respect to one another in the galaxy. Such catalogs often specify the star's position or that of the vernal equinox as of a particular date.
Sources and Citations
- Rukl, Antonin, "The Astronomer's Manual." Crescent Books, New York, NY, 1989.
- �"Star Identification." Naval Air Training Command, Navigation Section, 1951.
- Rodney Ruff, Omaha, NE; lifelong astronomy buff