Beta Scorpii is a multiple star system in the southern

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation whose recognition pred ...

. It bore the traditional proper name of Acrab , though the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

now regards that name as applying only to the β Scorpii Aa component.

Components

Observed through a small telescope, Beta Scorpii appears as a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

with a separation between the two components of 13.5 arcseconds and a combined

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 2.50. This pair, designated β¹ Scorpii and β² Scorpii, form the top branches of a hierarchy of six orbiting components.

Hierarchy of orbits in the β Scorpii system

β¹ Scorpii, the brighter of the pair, consists of two sub-components, designated β Scorpii A and β Scorpii B, orbiting at an angular separation of 0.3 arcseconds with an orbital period of 610 years. β Scorpii A is itself a

spectroscopic binary A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

, with the two components designated β Scorpii Aa (also named Acrab) and β Scorpii Ab. They are separated by 1.42 milliarcseconds and have an orbital period of 6.82 days. β² Scorpii also has two sub-components, designated β Scorpii C and β Scorpii E, orbiting at an angular separation of 0.1328 arcseconds with an orbital period of 39 years. β Scorpii E in turn is a spectroscopic binary with components designated β Scorpii Ea and β Scorpii Eb and having an orbital period of 10.7 days. Component β Scorpii D is the unrelated seventh magnitude star HD 144273, 520" away. Some authors have also referred to component Ab as D. A companion to component B, β Scorpii G, has been proposed to account for missing mass in the system, but no further evidence of its existence has been found. β Scorpii F refers to a theorised companion to component E.

Nomenclature

''Beta Scorpii'' is the star's

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

. This designation is Latinized from β Scorpii, and abbreviated Beta Sco or β Sco. ''β¹'' and ''β² Scorpii'' are those of its two components. The designations of the sub-components - ''β Scorpii A'', ''Aa'', ''Ab'', ''B'', ''C'', ''E'', ''Ea'' and ''Eb'' - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the

(IAU). Beta Scorpii bore the traditional names ''Acrab'', ''Akrab'' or ''Elacrab'', all deriving from the

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

name () ''al-'Aqrab'' 'the Scorpion' for the whole constellation, as well as Graffias , Italian for "the claws", a name it shared with Xi Scorpii. In 2016, the

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Acrab'' for the component ''β Scorpii Aa'' on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, (), meaning ''

Room In a building or a ship, a room is any enclosed space within a number of walls to which entry is possible only via a door or other dividing structure. The entrance connects it to either a passageway, another room, or the outdoors. The space is ...

'', refers to an asterism consisting of both of β¹ Scorpii and β² Scorpii, π Scorpii, ρ Scorpii and δ Scorpii, . Consequently, the

Chinese name Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethni ...

for both of β¹ Scorpii and β² Scorpii is (), "the Fourth Star of Room".

Namesake

USS Graffias (AF-29) was once a

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

navy ship named after the star.

Properties

The β Scorpii system is a kinematic member of the Upper Scorpius subgroup of the Scorpius–Centaurus association, a group of thousands of young stars with mean age 11 million years at distance 470 light years (145 parsecs). Analysis of β¹ Scorpii as a single star derived an evolutionary age between 9 and 12 million years, but analysis of the β Scorpii system as a whole suggest an age closer to 6 million years. The two components of β Scorpii A are the most massive members of the system, and respectively. The combined spectral type is B1 V. The individual spectral types cannot be clearly measured, but are estimated to be B0.5 and B1.5. Component Aa is evolving slightly away from the zero age main sequence and its

luminosity class In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...

is estimated to be intermediate between

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...

(IV) and

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

(V). Component Ab has a main sequence luminosity class, a temperature of 26,400 K, and a luminosity of . Component B is over 20 times fainter than the combined component A stars and a clear spectral type has not been measured. Its mass is estimated to be approximately . Component C has a stellar classification of B2 V and a mass of . It has an effective surface temperature of 24,000 K, a radius of and a bolometric luminosity of . Component E is determined to have a temperature of 13,000 K, radius of , and luminosity of . It is chemically peculiar, with high abundances of

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

and

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

. It is possibly a mercury-manganese (HgMn) star, but abundances of other metals are unexpectedly low. Beta Scorpii is 1.01 degree from the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

and can be occulted by the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

and, very rarely, by

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s. On December 9, 1906, it was occulted by

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

. The last

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

by a planet took place on 13 May 1971, by

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

Observation

On 11 December 2019, it had a close conjunction (geocentric separation <1') with Mercury.

In culture

Beta Scorpii appears on the

flag of Brazil The national flag of Brazil is a blue disc depicting a starry sky (which includes the Crux, Southern Cross) spanned by a curved band inscribed with the List of national mottos, national motto ('Order and Progress'), within a yellow rhombus, on ...

, symbolising the state of

Maranhão Maranhão () is a States of Brazil, state in Brazil. Located in the country's Northeast Region, Brazil, Northeast Region, it has a population of about 7 million and an area of and it is divided into 217 municipalities. Clockwise from north, it ...

References

External links

Beta Scorpii by Jim Kaler
* {{Stars of Scorpius Scorpii, Beta Spectroscopic binaries 6 B-type main-sequence stars Scorpius Acrab Upper Scorpius Scorpii, 08 5984 5 144217 8 078820 1 Durchmusterung objects Mercury-manganese stars