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Graffias, β Scorpii
Scorpius constellation map.png
Graffias is the top left "claw".
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scorpius
Right ascension 16h 05m 26.7s
Declination -19° 48' 20"
Apparent magnitude (V) 2.62/4.92 [1]
Characteristics
Spectral type B0.5V/B2V
U-B color index -0.07
B-V color index -0.08
Variable type ?
Astrometry
Radial velocity (Rv) -1 km/s
Proper motion (μ) RA: -6.75 mas/yr
Dec.: -24.89 mas/yr
Parallax (π) 6.15 ± 1.15 mas
Distance 530 ly
(163 pc)
Absolute magnitude (MV) β¹; -3.50
β²; -1.16
Details
Mass β¹; 10 [1] M
Radius 19 R
Luminosity β¹; 20,000 [1] L
Temperature β¹; 27 000 K
β²; 22 000 [1] K
Metallicity ?
Rotation ~130 km/s.
Age ? years
Other designations
Acrab, Elacrab, Graffias,[2] (Grafias[citation needed]), Grassias, 8 Scorpii, HR 5985, HD 144218, BD-19 4308, HIP 78821, SAO 159683, GC 21610, ADS 9913, CCDM 16054-1948

Beta Scorpii (β Sco / β Scorpii) is a star system in the constellation Scorpius. It has the traditional names Acrab, Akrab or Elacrab, all come from (Arabic: العقرب‎) al-'Aqrab, the Scorpion, for the whole constellation, as well as Graffias, a name it shares with Xi Scorpii. It was known as 房宿四 (the Fourth Star of the Room) in Chinese.

Observed through a small telescope, Beta Scorpii is found to be a binary star with a separation between the two components of 14 arcseconds, putting them at least 2200 Astronomical Units (AU) apart. They are both hot, B-class stars at least 10 times as massive as our own Sun, and will have short lives. Both are expected to end their stellar evolution in massive supernovae.

Beta-1 Scorpii, the brighter of the pair, has another companion 0.5 arcseconds, or about 80 AU, distant. Furthermore, both Beta-1 Scorpii and Beta-2 Scorpii, the two hot, B-class stars, are themselves thought to be spectroscopic binaries, bringing the total number of stars in the system to five.

Because it is close to the ecliptic, Beta Scorpii can be occulted by the Moon and, very rarely, by planets. The last occultation by a planet took place on 13 May 1971, by Jupiter.

References

  1. ^ a b c d Professor James B. (Jim) Kaler. "GRAFFIAS (Beta Scorpii)". University of Illinois. http://stars.astro.illinois.edu/sow/graffias.html. Retrieved 2010-02-20. 
  2. ^ Allen, R. H., (1899) Star-names and Their Meanings, New York: G. E. Stechert, p. 367.

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