Beta scorpio

Beta Scorpio (β Sco) is a multiple star system in the constellation Scorpio . It has several historical names:

• Akrab , Elakrab from the Arabic العقرب ( al-'Aqrab ) which means "scorpion" ^[1] .
• Graffias from the Arabic “claw” ^[2] , which she shares with Xi Scorpio .
• Raffias from the Greek "crab" ^[3] .

Akrab is quite bright (second magnitude ), but it is only the sixth brightest star in the constellation. Beta’s designation is probably due to its extreme position in the constellation. Through a small telescope, a classic double star is visible in which the components are separated by 14 seconds of the arc . The brighter and more western, β ¹ , has a magnitude of +2.62 ^m , the weaker, β², has a magnitude of +4.92 ^m . The distance between them is at least 2200 a. e. , and it takes them 16,000 years to complete one revolution around each other ^[4] .

Both stars are very hot, they belong to spectral class B: β ¹ has a temperature of about 27,000 K , β² about 22,000 K. Although both should appear white-blue to the eye, a rather large difference in brightness makes their color not so clear: a fainter star appears somewhat yellowish.

A more thorough study reveals a very complex structure of the star system. The β ¹ component is divided into β Sco A and β Sco B subcomponents. The dim β β Sco B subcomponent, which has a magnitude of about +10 ^m , is about 3.9 arc seconds apart from β Sco A and revolves around it for 610 years. Moreover, spectral studies show that β Sco A is a spectrally binary star composed of β Sco Aa and β Sco Ab components that revolve around their common center of gravity with a period of 6.82 days at a distance of 0.00142 arc seconds , which is 0.3 a. e. and comparable with the distance between the Sun and Mercury ^[5] . According to the agreement adopted by the Working Group on Star Names of the International Astronomical Union , the proper name of a star in the case of multiple stars is attributed to the brightest component ^{[6] [7]} , therefore, at present, the proper name Akrab is transferred to the component β Sco Aa ^[8] .

The main component β² is also divided into two subcomponents β Sco C and β Sco E with an angular separation of 0.1328 arc seconds and an orbital period of 39 years. In turn, β Sco E is a spectroscopically binary star (β Sco Ea and β Sco Eb) with a circulation period of 10.7 days. Thus, Akrab is at least a six-star system, and there are suggestions that the system includes one or even two stars ^{[9] [10]} . Of the six known components, at least 4 are hot stars of spectral class B, which indicates their simultaneous birth in the same place ^[4] .

Component β ^{1 is} more than 20,000 times brighter than the Sun. To survive in such a system, the Earth would have to be at a distance of 150 a. e. We would see the triple Sun, and β² would shine 50 times brighter than the full Moon . Both β ¹ stars are more than 10 times more massive than the Sun , and both are likely to explode in a few million years.

Akrab is located close to the ecliptic , therefore it can be covered by the moon , and very rarely by planets . Part of what is known about the system was obtained during the rare coverage of the β² component by the satellite of Jupiter Io ^[4] on May 14, 1971 at 2:00 UTC ^[11] .