Variable star in the constellation Hercules
Tau Herculis
Historical depiction of the constellation
Hercules with τ, bottom left, as the "northern knee"
Observation data
Epoch J2000
Equinox J2000
Constellation
Hercules
Right ascension
16h 19m 44.43666s
[1]
Declination
46° 18′ 48.1123″
[1]
Apparent magnitude (V)
3.91
[2] 3.83 to 3.86
[3]
Characteristics
Evolutionary stage
Main sequence
[4]
Spectral type
B5 IV
[5]
U−B
color index
−0.569
[2]
B−V
color index
−0.151± 0.009
[2]
Variable type
SPB
[3]
Astrometry
Radial velocity (Rv ) −15.5± 0.5
[2] km/s
Proper motion (μ)
RA: −13.33
[1]
mas /
yr
Dec.: 38.48
[1]
mas /
yr
Parallax (π) 10.61 ± 0.11
mas
[1]
Distance 307 ± 3
ly (94.3 ± 1.0
pc )
Absolute magnitude (MV ) −0.96
[2]
Details
Mass 4.01
[6]
M ☉
Radius 3.55± 0.19 R ☉
[7] 3.80± 0.25
[8]
R ☉
Luminosity 574
[2]
L ☉
Surface gravity (log g ) 4.02± 0.05
[7]
cgs
Temperature 15,615± 301
[7]
K
Metallicity [Fe/H]0.15
[9]
dex
Rotational velocity (v sin i ) 32
[6] km/s
Age 26
[6]
Myr
Other designations Rukbalgethi Shemali,
τ Her ,
22 Her ,
BD +46°2169 ,
FK5 608,
GC 21987,
HD 147394,
HIP 79992,
HR 6092,
SAO 46028,
CCDM J16197+4619A
[10]
Database references
SIMBAD
data
Tau Herculis , a name
Latinized from τ Herculis, is a
variable star in the northern
constellation of
Hercules . It has a blue-white hue and is visible to the naked eye at night with an
apparent visual magnitude that fluctuates around 3.91.
[2] The star is located at a distance of approximately 307
light years from the
Sun based on
parallax ,
[1] but it is drifting closer with a
radial velocity of −16 km/s.
[2]
A
light curve for Tau Herculis, plotted from
TESS data
[11]
The
stellar classification of Tau Hercules is B5 IV,
[5] and it serves as a standard
spectrum in the modern Morgan–Keenan (MK) classification.
[12] It is estimated to be just 26 million years old with a relatively low
projected rotational velocity of 32 km/s.
[6] Slowly rotating B-type stars are often
chemically peculiar , so the mostly normal spectra of this star suggests we may be viewing it from near pole-on.
[13] The abundance of most heavier elements in this star are about 85% of those in the Sun.
[14] The star has four times the
mass of the Sun
[6] and around 3.8
[8] times the
Sun's radius . On average, it is radiating 574
[2] times the
luminosity of the Sun from its
photosphere at an
effective temperature of 15,615 K.
[7]
During the
Hipparcos mission,
[4] Tau Hercules was discovered to be a
variable star of the
slowly pulsating B-type . These are
mid-B main sequence stars that vary with a period of about a day;
[4] the brightness of Tau Hercules varies by 0.03 magnitude
[3] over a period of 1.24970± 0.00008 days. The radial velocity of the star varies at a different rate than the
photometric period, with the object showing both radial and non-radial pulsation modes.
[4]
[15]
Historical significance and etymology
The path of the north celestial pole among the stars due to the precession.
Tau Herculis is located within 1° of the
precessional path traced across the
celestial sphere by the Earth's
North pole . It could have served the northern
pole star around the year 7400 BCE, a phenomenon which is expected to reoccur in the year 18,400 due to
precession .
[13]
Its traditional name, Rukbalgethi Shemali , is of Arabic origin and shares certain etymological characteristics with the stars
Ruchbah and
Zubeneschamali , signifying Hercules' "northern knee".
[16] [
better source needed ]
In
Chinese , 七公 (Qī Gōng ), meaning
Seven Excellencies , refers to an asterism consisting of τ Herculis,
42 Herculis ,
φ Herculis ,
χ Herculis ,
ν1 Boötis ,
μ1 Boötis and
δ Boötis .
[17] Consequently, the
Chinese name for τ Herculis itself is 七公二 (Qī Gōng èr , English: the Second Star of Seven Excellencies .)
[18]
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
e
f
g
h
i Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters , 38 (5): 331,
arXiv :
1108.4971 ,
Bibcode :
2012AstL...38..331A ,
doi :
10.1134/S1063773712050015 ,
S2CID
119257644 .
^
a
b
c Samus', N. N; et al. (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports , 61 (1): 80,
Bibcode :
2017ARep...61...80S ,
doi :
10.1134/S1063772917010085 ,
S2CID
125853869 .
^
a
b
c
d Masuda, Seiji; Hirata, Ryuko (April 2000), "Line-profile variation in tau Herculis", Astronomy and Astrophysics , 356 : 209–212,
Bibcode :
2000A&A...356..209M .
^
a
b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics , 11 : 29,
Bibcode :
1973ARA&A..11...29M ,
doi :
10.1146/annurev.aa.11.090173.000333 .
^
a
b
c
d
e David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal , 804 (2): 146,
arXiv :
1501.03154 ,
Bibcode :
2015ApJ...804..146D ,
doi :
10.1088/0004-637X/804/2/146 ,
S2CID
33401607 .
^
a
b
c
d Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal , 129 (3): 1642–1662,
arXiv :
astro-ph/0412542 ,
Bibcode :
2005AJ....129.1642F ,
doi :
10.1086/427855 ,
S2CID
119512018 .
^
a
b Gordon, Kathryn D.; et al. (2019), "Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array", The Astrophysical Journal , 873 (1): 91,
Bibcode :
2019ApJ...873...91G ,
doi :
10.3847/1538-4357/ab04b2 ,
S2CID
125181833 .
^ Smith, K. C.; Dworetsky, M. M. (1993), "Elemental Abundances in Normal Late B-Stars and Hgmn-Stars from Co-Added IUE Spectra - Part One - Iron Peak Elements", Astronomy and Astrophysics , 274 (2): 335,
Bibcode :
1993A&A...274..335S
^
"* tau Her" .
SIMBAD .
Centre de données astronomiques de Strasbourg . Retrieved 2010-06-10 .
^
MAST: Barbara A. Mikulski Archive for Space Telescopes , Space Telescope Science Institute, retrieved 24 September 2022 .
^ Garcia, B. (June 1989), "A list of MK standard stars", Bulletin d'Information du Centre de Donnees Stellaires , 36 : 27,
Bibcode :
1989BICDS..36...27G .
^
a
b
Kaler, James B. ,
"TAU HER (Tau Herculis)" , Stars ,
University of Illinois , retrieved 2018-04-27 .
^ Adelman, Saul J.; et al. (June 2001), "Elemental abundance analyses with DAO spectrograms. XXV. The superficially normal B and A stars alpha Draconis, tau Herculis, gamma Lyrae, and HR 7926", Astronomy and Astrophysics , 371 (3): 1078–1083,
Bibcode :
2001A&A...371.1078A ,
doi :
10.1051/0004-6361:20010408
^ Briquet, M.; et al. (April 2003), "Spectroscopic mode identification for the slowly pulsating B star HD 147394", Astronomy and Astrophysics , 401 : 281–288,
Bibcode :
2003A&A...401..281B ,
doi :
10.1051/0004-6361:20030086 .
^ Kurt Vonnegut.
"Constellations: Hercules 'the Strongman' " . The BBC (British Broadcasting Corporation). Retrieved 2010-11-14 .
^ (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)
AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日