Beta Scorpii

Location of β Scorpii (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Scorpius
HR 5984
Right ascension	16h 05m 26.23198s[1]
Declination	–19° 48′ 19.6300″[1]
Apparent magnitude (V)	2.63[2]
HR 5985
Right ascension	16h 05m 26.57128s[1]
Declination	–19° 48′ 06.8556″[1]
Apparent magnitude (V)	4.92[2]
Characteristics
Spectral type	B0.5V + B2V[3]
U−B color index	–0.08 / –0.70[2]
B−V color index	–0.08 / –0.02[2]
Astrometry
HR 5984
Radial velocity (Rv)	–1.0[4] km/s
Proper motion (μ)	RA: –5.20[1] mas/yr Dec.: –24.04[1] mas/yr
Parallax (π)	8.07 ± 0.78[1] mas
Distance	400 ± 40 ly (120 ± 10 pc)
HR 5985
Radial velocity (Rv)	–3.6[4] km/s
Proper motion (μ)	RA: –5.07[1] mas/yr Dec.: –25.87[1] mas/yr
Parallax (π)	8.19 ± 1.17[1] mas
Distance	400 ± 40 ly (approx. 120 pc)
Details
HR 5984
Mass	10[5] M☉
Radius	19 R☉
Luminosity	20,000[5] L☉
Temperature	27,000[5] K
Rotational velocity (v sin i)	100[6] km/s
HR 5985
Temperature	22,000[5] K
Rotational velocity (v sin i)	65[6] km/s
Other designations
Acrab, Elacrab, Graffias,[7] Grassias, 8 Scorpii, ADS 9913. A: β1 Sco, BD–19 4307, HD 144217, HIP 78820, HR 5984, SAO 159682. B: β2 Sco, BD–19 4308, HD 144218, HIP 78821, HR 5985.

Beta Scorpii (β Sco, β Scorpii) is a multiple star system in the southern zodiac constellation of 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.

Fixed typo "hierarchy" of orbits in the Beta Scorpii system.^[8]

Observed through a small telescope, Beta Scorpii appears as a binary star with a separation between the two components of 13.5 arcseconds. This pair, β¹ and β², form the top branches of the hierarchy of orbiting components in this system. β¹ Scorpii, the brighter of the pair, consists of two sub-components, β Sco A and β Sco B, orbiting at an angular separation of 3.9 arcseconds with an orbital period of 610 years. β Sco A is itself a spectroscopic binary with the components β Sco Aa and β Sco Ab separated by 1.42 milliarcseconds and an orbital period of 6.82 days.^[8]

The second visual component, β² Scorpii, has two sub-components, β Sco C and β Sco E, orbiting at an angular separation of 0.1328 arcseconds with an orbital period of 39 years. β Sco E is a spectroscopic binary with the components β Sco Aa and β Sco Ab having an orbital period of 10.7 days. This brings the total number of stars in the system to six. There is no D component; this is now an artifact of earlier system models.^[8]

The two most massive members of the system have the spectrum of B-type main sequence stars. Component C has a stellar classification of B2V.^[8] They are both hot stars at least 10 times as massive as our own Sun, and will have short lives. Both are expected to end their stellar evolution with massive Type II supernova explosions.

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.

In culture [link]

Graffias appears on the flag of Brazil, symbolising the state of Maranhão.^[9] USS Graffias (AF-29) is once of United States navy ship.

References [link]

External links [link]

• Graffias
• Image of Graffias from APOD