Star in the constellation Scorpius
ε Scorpii
Location of ε Sco (circled)
Observation data
Epoch J2000
Equinox J2000
Constellation
Scorpius
Right ascension
16h 50m 09.8s
[1]
Declination
–34° 17′ 36″
[1]
Apparent magnitude (V)
+2.310
[2] (2.24 - 2.35)
[3] )
Characteristics
Spectral type
K1 III
[4]
U−B
color index
+1.147
[2]
B−V
color index
+1.150
[2]
Variable type
suspected
[3]
Astrometry
Radial velocity (Rv ) –2.5
[5] km/s
Proper motion (μ)
RA: –614.85
[1]
mas /
yr
Dec.: –255.98
[1]
mas /
yr
Parallax (π) 51.19 ± 0.22
mas
[1]
Distance 63.7 ± 0.3
ly (19.54 ± 0.08
pc )
Absolute magnitude (MV ) 0.78 ± 0.04
[6]
Details
Mass 1.24
[7]
M ☉
Radius 12.6
[8]
R ☉
Surface gravity (log g ) 2.49
[9]
cgs
Temperature 4,560
[9]
K
Metallicity [Fe/H]–0.17
[9]
dex
Rotational velocity (v sin i ) 2.6 ± 0.5
[10] km/s
Other designations Wei, Larawag, 26 Scorpii,
CD –34 11285,
FK5 628,
GCTP 3823.00,
Gl 639.1,
HD 151680,
HIP 82396,
HR 6241,
LHS 3244,
SAO 208078.
[11]
Database references
SIMBAD
data
Epsilon Scorpii (ε Scorpii , abbreviated Eps Sco , ε Sco ), formally named Larawag ,
[12] is a
star in the southern
zodiac
constellation of
Scorpius . It has an
apparent visual magnitude of +2.3,
[2] making it the fifth-brightest member of the constellation.
Parallax measurements made during the
Hipparcos mission provide an estimated distance to this star of around 63.7
light-years (19.5
parsecs ) from the
Sun .
[1]
Epsilon Scorpii has a
stellar classification of K1 III,
[4] which indicates it has exhausted the supply of hydrogen at its core and
evolved into a
giant star . The
interferometry -measured
angular diameter of this star, after correcting for
limb darkening , is 5.99 ± 0.06
mas ,
[13] which, at its estimated distance, equates to a physical radius of nearly 13 times the
radius of the Sun .
[8] Presently it is generating energy through the
nuclear fusion of helium at its core, which, considering the star's composition, places it along an evolutionary branch termed the
red clump .
[14] The star's outer atmosphere has an
effective temperature of 4,560 K,
[9] giving it the orange hue of a cool
K-type star .
ε Scorpii is classified as a suspected
variable star ,
[3] although a study of
Hipparcos photometry showed a variation of no more than 0.01–0.02 magnitudes.
[14] It is an X-ray source with a luminosity of (1.5–1.6) × 1027 erg s−1 .
[6]
[15]
Nomenclature
ε Scorpii (
Latinised to Epsilon Scorpii ) is the star's
Bayer designation .
The star bore the traditional name Larawag in the culture of the
Wardaman people of the
Northern territory of
Australia ,
[16] meaning clear sighting .
[17] In 2016, the IAU organized a
Working Group on Star Names (WGSN)
[18] to catalog and standardize proper names for stars. The WGSN approved the name Larawag for Epsilon Scorpii on 19 November 2017 and it is now so included in the List of IAU-approved Star Names.
[12]
Patrick Moore introduced the name Wei as
Chinese name for this star.
[19] However, this seems to be a misreading, as
Chinese 尾宿 (Wěi Xiù , English
Tail ) refers to an
asterism (i.e.
Chinese constellation ) consisting of Epsilon Scorpii,
Mu¹ Scorpii ,
Zeta¹ Scorpii and
Zeta² Scorpii ,
Eta Scorpii ,
Theta Scorpii ,
Iota² Scorpii and
Iota¹ Scorpii ,
Kappa Scorpii ,
Lambda Scorpii and
Upsilon Scorpii .
[20] Consequently, the name for Epsilon Scorpii itself is 尾宿二 (Wěi Xiù èr ), which means "the Second Star of Tail".
[21]
[22]
In culture
Epsilon Scorpii appears on the
flag of Brazil , symbolising the state of
Ceará .
[23]
References
^
a
b
c
d
e
f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics , 474 (2): 653–664,
arXiv :
0708.1752 ,
Bibcode :
2007A&A...474..653V ,
doi :
10.1051/0004-6361:20078357 ,
S2CID
18759600
^
a
b
c
d Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement , 15 : 459,
Bibcode :
1968ApJS...15..459G ,
doi :
10.1086/190168
^
a
b
c Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S . 1 : 02025.
Bibcode :
2009yCat....102025S .
^
a
b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample",
The Astronomical Journal , 132 (1): 161–170,
arXiv :
astro-ph/0603770 ,
Bibcode :
2006AJ....132..161G ,
doi :
10.1086/504637 ,
S2CID
119476992
^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg , 35 (35), Astronomisches Rechen-Institut Heidelberg: 1,
Bibcode :
1999VeARI..35....1W
^
a
b Schroeder, K.-P.; Huensch, M.; Schmitt, J. H. M. M. (July 1988), "X-ray activity and evolutionary status of late-type giants", Astronomy and Astrophysics , 335 : 591–595,
Bibcode :
1998A&A...335..591S
^ Fuhrmann, K; Chini, R; Kaderhandt, L; Chen, Z (2017).
"Multiplicity among Solar-type Stars" . The Astrophysical Journal . 836 (1): 139.
Bibcode :
2017ApJ...836..139F .
doi :
10.3847/1538-4357/836/1/139 .
^
a
b Lang, Kenneth R. (2006),
Astrophysical formulae , Astronomy and astrophysics library, vol. 1 (3rd ed.),
Birkhäuser ,
ISBN
3-540-29692-1 . The radius (R* ) is given by:
2
⋅
R
∗
=
(
10
−
3
⋅
19.54
⋅
5.99
)
AU
0.0046491
AU
/
R
⨀
≈
25.2
⋅
R
⨀
{\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(10^{-3}\cdot 19.54\cdot 5.99)\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 25.2\cdot R_{\bigodot }\end{aligned}}}
^
a
b
c
d McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants", Astrophysical Journal Supplement Series , 74 : 1075–1128,
Bibcode :
1990ApJS...74.1075M ,
doi :
10.1086/191527
^ Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal , 135 (3): 892–906,
arXiv :
0711.4984 ,
Bibcode :
2008AJ....135..892C ,
doi :
10.1088/0004-6256/135/3/892 ,
S2CID
2756572
^
"eps Sco" .
SIMBAD .
Centre de données astronomiques de Strasbourg . Retrieved 2012-02-23 .
^
a
b
"Naming Stars" . IAU.org. Retrieved 16 December 2017 .
^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics , 431 (2): 773–777,
Bibcode :
2005A&A...431..773R ,
doi :
10.1051/0004-6361:20042039
^
a
b Adelman, Saul J. (2001), "On the Photometric Variability of Red Clump Giants", Baltic Astronomy , 10 (4): 593–597,
Bibcode :
2001BaltA..10..593A ,
doi :
10.1515/astro-2001-0404
^ Gondoin, P. (December 1999), "Evolution of X-ray activity and rotation on G-K giants", Astronomy and Astrophysics , 352 : 217–227,
Bibcode :
1999A&A...352..217G
^
"IAU Approves 86 New Star Names From Around the World" (Press release). IAU.org. 11 December 2017.
^
"IAU Working Group on Star Names (WGSN)" (Press release). IAU.org.
^
"IAU Working Group on Star Names (WGSN)" . Retrieved 22 May 2016 .
^ Moore, P. (1983), The Guinness Book of Astronomy: Facts (2nd ed.), Middlesex, UK: Guinness Superlatives Limited, p. 242
^ (in Chinese) 中國星座神話 , written by 陳久金. Published by 台灣書房出版有限公司, 2005,
ISBN
978-986-7332-25-7 .
^ (in Chinese)
香港太空館 - 研究資源 - 亮星中英對照表
Archived 2008-10-25 at the
Wayback Machine , Hong Kong Space Museum. Accessed on line November 23, 2010.
^
Ridpath, Ian ,
Star Tales .
^
"Astronomy of the Brazilian Flag" . FOTW Flags Of The World website.