Flamsteed designation
Flamsteed designations for star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s are similar to Bayer designation
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name...

s, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 it lies in (see List of constellations for a list of constellations and the genitive forms of their names). Flamsteed designation contained 2554 stars.

The numbers were originally assigned in order of increasing right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...

 within each constellation, but due to the effects of precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

 they are now slightly out of order in some places. This method of designating stars first appeared in a preliminary version of John Flamsteed
John Flamsteed
Sir John Flamsteed FRS was an English astronomer and the first Astronomer Royal. He catalogued over 3000 stars.- Life :Flamsteed was born in Denby, Derbyshire, England, the only son of Stephen Flamsteed...

's Historia Coelestis Britannica which was published by Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

 and Isaac Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

 in 1712 without Flamsteed's approval. The final version of Flamsteed's catalogue published in 1725 after his death omitted any number designations altogether.

The designations gained popularity throughout the eighteenth century, and are now commonly used when no Bayer designation exists; however, where a Bayer designation does exist for a star it is used almost exclusively and the Flamsteed designation is almost never used. Examples of well-known stars which are usually referred to by their Flamsteed numbers include 51 Pegasi
51 Pegasi
51 Pegasi is a Sun-like star located 15.6 parsecs from Earth in the constellation Pegasus...

 (see Extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

), and 61 Cygni
61 Cygni
61 Cygni,Not to be confused with 16 Cygni, a more distant system containing two G-type stars harboring the gas giant planet 16 Cygni Bb. sometimes called Bessel's Star or Piazzi's Flying Star, is a binary star system in the constellation Cygnus...

 (see Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

). Flamsteed designations do, however, tend to trump the Bayer designation if the latter contains an extra attached number, so "55 Cancri
55 Cancri
55 Cancri , also cataloged Rho1 Cancri or abbreviated 55 Cnc, is a binary star approximately 41 light-years away from Earth in the constellation of Cancer...

" is more common than "Rho-1 Cancri".

There are examples of stars bearing Flamsteed designations for constellations in which they do not lie, just as there are for Bayer designations, because of the compromises that had to be made when the modern constellation boundaries were drawn up.

It should also be noted that Flamsteed's catalogue covered only the stars visible from Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

, and therefore stars of the far southern constellations have no Flamsteed numbers. Some stars, such as the nearby star 82 Eridani
82 Eridani
82 G. Eridani is a star about 20 light years away from Earth. It is in the constellation Eridanus. It is a main sequence star of spectral type G5.-Observation:...

, were named in a major southern-hemisphere catalog called Uranometria Argentina, by Benjamin Gould, and are not true Flamsteed numbers, and should properly contain a G, as in 82 G. Eridani. Apart from a handful of cases, these designations are not currently in use.

Some entries in Flamsteed's catalog are errors: for instance, Flamsteed observed Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...

 in 1690 but did not recognize it as a planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

 and entered it into his catalog as a star called "34 Tauri".

List of constellations utilizing Flamsteed star designations

There are 52 constellations that primarily utilize Flamsteed designations. Stars are listed in the appropriate lists for the constellation, as follows:

See also

  • Star designation
    Star designation
    Designations of stars are done by the International Astronomical Union . Many of the star names in use today were inherited from the time before the IAU existed. Other names, mainly for variable stars , are being added all the time.Approximately 10,000 stars are visible to the naked eye...

Flamsteed objects
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