Delta Scorpii

δ Scorpii

Template:Location mark Location of δ Scorpii (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Scorpius
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	1.59 - 2.32
Characteristics
Spectral type	B0.3 IV + B1-3V
U−B Template:Engvar	−0.920
B−V Template:Engvar	−0.124
Variable type	γ Cas
Astrometry
Radial velocity (Rv)	−7 km/s
Proper motion (μ)	RA: −10.21 mas/yr Dec.: −35.41 mas/yr
Parallax (π)	6.64±0.89 mas
Distance	136.0 pc
Absolute magnitude (MV)	−3.8
Orbit
Period (P)	Template:Val yr
Semi-major axis (a)	Template:Val" (Template:Val)
Eccentricity (e)	Template:Val
Inclination (i)	Template:Val°
Longitude of the node (Ω)	Template:Val°
Periastron epoch (T)	2011 July 3rd
Argument of periastron (ω) (secondary)	Template:Val°
Semi-amplitude (K1) (primary)	Template:Val km/s
Details
δ Sco A
Mass	13 Template:Solar mass
Radius	8.5 Template:Solar radius
Luminosity	38,000 Template:Solar luminosity
Surface gravity (log g)	3.92 cgs
Temperature	27,400 K
Rotational velocity (v sin i)	180 km/s
δ Sco B
Mass	8.2 Template:Solar mass
Temperature	20-24,000 K
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Age	9-10 Myr
Other designations
Dschubba, Dzuba, Al Jabba, Iclarkrau, 7 Scorpii, BD−22°4068, HD 143275, HIP 78401, HR 5953, FK5 594, SAO 184014, CCDM 16003-2237
Database references
SIMBAD	data

Delta Scorpii (Latinised from δ Scorpii, abbreviated Delta Sco, δ Sco) is a binary star (the presence of a third star in the system is being debated) in the constellation of Scorpius. The primary star is named Dschubba Template:IPAc-en.

Observation

File:DeltaScoLightCurve.png

A visual band light curve for Delta Scorpii. The main plot (adapted from Suffak et al.) shows the long-term variability, and the inset plot (adapted from Miroshnichenko et al.) shows the brightening which occurred in 2000.

Delta Scorpii is 2.0 degrees south of the ecliptic. It is a binary star with two components of magnitudes 2.4 and 4.6 separated by Template:Val. In 1981 it was occulted by Saturn's rings as seen by Voyager 2, with starlight unexpectedly blocked even by the apparently empty gaps, indicating that "there is very little empty space anywhere in the main ring system."

Variability

Delta Scorpii A is a Gamma Cassiopeiae variable star. This type of star shows irregular slow brightness variations of a few hundredths of a magnitude due to material surrounding the star.

In June 2000 Delta Scorpii was observed by Sebastian Otero to be 0.1 magnitudes brighter than normal; its brightness has varied since then and has reached at least as high as magnitude 1.6, altering the familiar appearance of Scorpius. Spectra taken after the outburst began have shown that the star is throwing off luminous gases from its equatorial region. The companion passed close by in 2011, again resulting in the star peaking at 1.65 between 5 and 15 July 2011.

Nomenclature

File:Rho Ophiucus Widefield.jpg

ρ Ophiuchi region. δ Scorpii is the bright white star on the left (north is down).

δ Scorpii (Latinised to Delta Scorpii) is the system's Bayer designation. The two components are designated Delta Scorpii A and B.

Delta Scorpii bore the traditional name Dschubba, which comes from Arabic جبهة العقرب jabhet al-aqrab meaning 'the forehead of the scorpion'. In 2016 the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Dschubba for δ Scorpii A on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.

In Chinese, (), meaning Room, refers to an asterism consisting of δ Scorpii, β¹ Scorpii, β² Scorpii, π Scorpii, and ρ Scorpii. Consequently, the Chinese name for δ Scorpii itself is (), "the Third Star of Room".

Properties

δ Scorpii was once used as a spectroscopic standard for the B0 IV classification, but is now considered too unusual and variable.

The primary, δ Scorpii A, is a B class subgiant surrounded by a disc of material spun off by the rapidly rotating star. The secondary, δ Scorpii B, orbits every 10.5 years in a highly elongated elliptical orbit; it appears to be a normal B class main sequence star. There have been reports that Delta Scorpii A is itself a very close spectroscopic binary, but this does not appear to be the case.

δ Scorpii is a proper motion member of the Upper Scorpius subgroup of the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. The Upper Scorpius subgroup contains thousands of young stars with mean age 11 million years at average distance of 470 light years (145 parsecs).

External links

• Jim Kaler's Stars, University of Illinois: Dschubba
• Delta Scorpii brighter than ever (Sky and Telescope, February 4, 2002)
• Delta Scorpii still showing off (Sky and Telescope, June 25, 2003)
• Delta Scorpii: the birth of a Be star (AAVSO article)