The 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...

 Beta Sagittarii (β Sgr, β Sagittarii) is shared by two star system

Star system

A star system or stellar system is a small number of stars which orbit each other, bound by gravitational attraction. A large number of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems.-Binary star systems:A stellar...

s, β¹ Sagittarii and β² Sagittarii, in the constellation

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....

 Sagittarius

Sagittarius (constellation)

Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...

. The two stars are separated by 0.36° in the sky. Beta Sagittarii also has the traditional name Arkab, from the Arabic

Arabic language

Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 عرقوب ^carqūb meaning hamstring.

β¹ Sagittarii

Beta-1 Sagittarii, also called Arkab Prior since it leads β² across the sky, is a binary star

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 lying 378 light years

Light Years

Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....

 from Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. Arkab Prior A is a spectral type

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 B9 main sequence

Main sequence

The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 dwarf which has an apparent magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of +3.96. Arkab Prior B is a type A3 dwarf with an apparent magnitude of +7.4. The two stars are separated in the sky by 28 arcseconds, which puts them at least 3300 astronomical units apart.

β² Sagittarii

Beta-2 Sagittarii, also called Arkab Posterior since it trails β¹ across the sky, is a spectral type

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 F2 giant

Giant star

A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...

 which has an apparent magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 of +4.27. It is 137 light years from Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

.

Namesakes

USS Arkab (AK-130)

USS Arkab (AK-130)

USS Arkab was an Crater-class cargo ship commissioned by the U.S. Navy for service in World War II, named after Arkab, the star in constellation Sagittarius...

 was a United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 Crater class cargo ship

Crater class cargo ship

Crater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....

named after the star.