The method of naming stars

In ancient times, only the sun and moon, a few visible stars, and planets had names. Each nation and region gave a special name to these objects. For example, 3600 names have been mentioned for the moon in astronomical sources around the world, some of which are familiar to us, such as Maah, Qamar, Ur, Taipei, Lune, etc.

By referring to the ancient history of various countries, we realize that efforts have been made in the past, but due to the lack of optical instruments, only a few known stars had special names, and the rest had different names, even in one country, due to the lack of communication facilities and the absence of Comprehensive standards mentioned several names for one star. Although some of these special names were historical, most of these names were often transcribed or translated from Arabic or Chinese names due to the domination and conquests of that time and were imported to other parts of the world, even to the books of European countries, whose works can still be found in astronomical maps.

Names such as the star Alcore (derived from the Arabic word Alkor in the constellation Ursa Major), the star Rigel (derived from the word Rajol, meaning man in the constellation Orion), the star Fomalhaut (alpha of the constellation Pisces, derived from the word Fam Alhut, meaning the mouth of a fish) And... Such transliteration can be different and there are different spellings for it. A smaller number of names have been introduced since the Middle Ages, and a few have been popularly used as nicknames in modern times, for example, Sualocin for α Delphinus and Navi for γ Cassiopeia. Also, Hipparchus in the 2nd century BC counted about 850 unarmed stars. Johann Bayer in 1603 mentioned about twice this number, and in the 19th century numerous catalogs were published under the title of visible stars.

On the other hand, due to the lack of standards, some names were used for several stars. For example, for most astronomy enthusiasts, "Deneb" means the brightest star of the Cygnus constellation, but the same name was placed on at least five other stars in the past. Even in the matter of constellations, although the visualization of some of them dates back to the very distant past, some stars are mentioned for two constellations.

Today, with the construction of advanced telescopes and the use of electronic tools, and the sending of space telescopes into Earth orbits, such as the Hubble Space Telescope and the James Webb Space Telescope, the number of detected astronomical objects has increased from thousands to more than billions of objects, and more are discovered every year. Therefore, astronomers should be able to identify all these objects without ambiguity, to determine a single and systematic naming method, which is indicative of the nature of the object and has a scientific meaning and concept.

Method of Bayer nomenclature (Atlas Uranometria):

German amateur astronomer Johann Bayer (1572-1625) prepared and published a star map called Uranometria in 1603, which is still used by amateur astronomers. In this naming method, the brightest star of each constellation is named Alpha, the second brightest is Beta, the third is Gamma, and so on. This atlas included 51 tables. Forty-eight tables related to the constellations of the northern hemisphere, one table containing the 12 newly discovered constellations at that time of the southern hemisphere, and two other tables containing all the northern and southern parts of the celestial sphere.

In short, Johann Bayer in this way:

1- Identified each star based on its brightness.

2- He assigned one of the small Greek letters from alpha to omega to each star.

3- He used small Latin letters for the rest of the stars.

Note: He did not use the letters j and u, which could be confused with i and v.

4- Finally, he placed the name of the constellation after this letter.

?Bugs:

1- Naming some stars under one name

2- Limitation on the number of Greek and Latin letters

3- The difficulty of grading faint stars and the error in this process

However, due to the ease of finding stars in this method, the new stars added after Johann Bayer was still named and classified with this method, and this reference is printed in three volumes and is available to astronomers today.

Naming stars by Flamsteed method:

In 1712 John Flamsteed, an astronomer of the Royal Astronomical Society of England, began to name the stars of each constellation from east to west according to their dimension, which was a great help in finding a star on a map.

In this naming system, for example, 80 Taurus is placed on the east side of 79 Taurus and on the west side of 81 Taurus. (Many years have passed since Flamsteed invented this system, but the coordinate system he used still corresponds well with celestial east and west.)

All stars were numbered regardless of whether they had Greek letters or not, which is why, for example, Alpha Lyra is also called 3 Lyra. All 2,682 stars received a Flamsteed number. The highest Flamsteed number in the Taurus constellation is 140 Taurus.

But when the boundaries of the constellations were defined in 1930, a group of stars numbered by Flamsteed was placed outside their constellation. For example, the star of 30 Monoceros was placed in the constellation of Hydra and the star of 49 Serpens was placed in the constellation of Hercules. Therefore, the use of this method gradually became obsolete after 1930 due to the publication of new astronomical books and the non-use of these tables.

In short, Flamsteed's classification method was done as follows:

1- Numbers were used instead of Greek and Latin lowercase letters.

2- Instead of classification based on the brightness of the stars of a constellation, the position of the star in that constellation from west to east was used as a criterion.

Naming by Arglander method:

Argelander and his successor divided the sky into one-degree declination ranges covering 24 hours. The stars in each range were named according to their dimension and the constellations the stars were in were ignored. In the Argelander nomenclature, the catalog numbers are determined by counting the stars in a certain inclination from north to south. Therefore, BD numbers represent the declination along with an ascending number based on the star count in this particular declination. For example, BD + 31° 216 means 216 stars in the range of declination +31 and +32.

The original BD covered only half of the sky, from the North Pole to -2° declination. A more southerly supplementary index called SBD expanded its range to -23 declination.

The Cordoba Durchmusterung (CD or CoD) catalog finished the job, collecting another 613,953 stars up to the celestial south pole.

Later, with the increase in the power of the telescopes, the CD list was more complete and was compiled under the title Durchmusterung or DM with the number of 1,071,800 stars.

Henry Draper naming method:

In this catalog, stars brighter than magnitude 8.5 and slightly fainter are classified and named according to color and spectral class. For example, HD183143.Later, more stars were added by the Henry Draper Extension. This list includes HDE and a number in front of it.

Photograph of the oxygen spectrum compared to the solar spectrum, by Henry Draper, 1877 (Linda Hall Library)

Revised Harvard Photometry:

In 1908, another catalog called Revised Harvard Photometry was prepared to obtain the exact magnitude of 9110 bright stars. This catalog searched for magnitudes up to about 6.5. Stars brighter than magnitude 6.5 are identified by a number that increases as the dimension increases. The prefix HR or BS is written in front of this number. For example, HR1099.

List of SAO

Another star numbering system in use today is called SAO, and it is related to the Smithsonian Astrophysical Observatory star catalog (1966), which was also prepared (using sky maps) at Harvard University. The SAO catalog gives very precise positions of 258,997 stars to about 9th magnitude.

Guide Star Catalog

One of the largest new catalogs is the Hubble Space Telescope's Guide Star Catalog, which is too large to print and is being released on compact discs. The position of stars of the GSC catalog has been measured with an accuracy of close to a minute of arc and a magnitude of a few tenths for 18,819,291 masses. The brightest star in this list is of magnitude 9. Despite the large number of stars in this catalog, recently other catalogs such as Hipparcos and Tycho have taken the place of the GSC Million Bright Stars list.

As you know, there are different types of stars, some of them are double, triple, and multiple, and some are variable. Since it is possible to see these stars mostly with a telescope, it was felt necessary to create a way to name them years ago. In the following, the method of naming this type of stars is explained.

The method of naming double and multiple stars:

The components of a binary or multiple set, if they have a recognizable distance from each other, are named using numbers and based on the west-east position. For example, Alpha Librae is a binary set with cleanable components. The western component of this set is called Alpha-1 and the eastern component is called Alpha-2. In such collections, moving to the east, these numbers will increase.

In multiple systems (or binary systems) when the components of the set are very close to each other, the brightness of the components is the naming criterion. In this way, the star that is the brightest star and the main component of the set continues with A and the fainter star continues with B. For example, Sirius itself is part of a binary system and its companion star is a white dwarf star. The night star, which is easily seen with the naked eye, has component A and its companion white dwarf is called B.

Method of naming variable stars:

This method is also known as Arglander's method. He named the first variable star he found in a constellation R. The next variable S and finally Z continued this work. After Z, he returned to R and placed it next to the previous R, i.e., RR (you are familiar with the name of the star RR Lyra, which is named accordingly.)

R – S – T – U – V – W – X – Y – Z

RR – RS – RT – RU – RV – RW – RX – RY – RZ

SS – ST – SU – SV - …

TT – TU – TV - …

UU – UV …

.

ZZ

Due to the fact that based on the telescopes of that time, up to this number of variables could be found in a constellation, Arglander continued this method to this extent. But years later, as more powerful telescopes were built and more variable stars were found in each constellation, astronomers decided to return to the letter A after ZZ and repeat the above process.

AA – AB – AC - … - AZ

BB – BC - … - BZ

.

.

.

QQ – QR – QS – QT - … - QZ

The letter J was removed because it could be confused with I in some languages.

The new method of naming variable stars:

1- The first variable star discovered in any constellation, if it is not named according to the Bayer or Flamsteed criteria, is called with the letter R followed by the name of the constellation.

?For example, the first variable star that was found in the constellation Cetus and was not named according to Bayer and Flamsteed's criteria was named R Ceti.

2- The second star discovered in that constellation is named S, then T, and so on until Z. This rule names the first nine stars discovered in each constellation.

?3- For the 10th star, name RR, then RS, then RT, and so on until RZ, then SS and ST, and so on until SZ, until we reach ZZ. This collection also names 54 variable stars in each constellation.

4- To continue, we start from AA and in the same way before to AZ and then BB to BZ. We keep doing this until we reach QZ. So far, 334 stars have been named.

5- To continue from the letter V along with a number starting from 335, we follow the work.

?For example, V335, V336, and...

In the end, while stating this, there are other catalogs for naming stars, but due to their incomprehensibility and lack of use in astronomy reference books, they have been omitted. Also, for non-stellar objects such as nebulae, galaxies, and clusters, there are catalogs such as the Messier and NGC catalogs, which are not mentioned because they do not have a scientific structure for naming and are the only numbers that are named after the discovery of each object. The purpose of this article was to answer the question of students about the reason why some numbers and letters are mentioned behind the names of the stars, and I hope this article is an answer to their questions.