Zeta1 Scorpii

Zeta1 Scorpii (Zeta1 Sco, ζ1 Scorpii, ζ1 Sco) is a B-type hypergiant star in the constellation of Scorpius.[9] It has an apparent visual magnitude which varies between 4.66 and 4.86.[3] It is a member of the Scorpius OB1 association,[10] and the open star cluster NGC 6231, also known as the "northern jewel box" cluster. Around 36 times as massive as the Sun, it is also one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity of around 850,000 times that of the Sun and a radius 103 times that of the Sun.[4]

For other stars with this Bayer designation, see Zeta Scorpii.
ζ1 Scorpii
Location of ζ1 Scorpii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Scorpius
Right ascension  16h 53m 59.72650s[1]
Declination −42° 21′ 43.3063″[1]
Apparent magnitude (V) 4.705[2] (4.66 to 4.86)[3]
Characteristics
Spectral type B1.5 Iae[4]
U−B color index −0.567[2]
B−V color index +0.480[2]
Variable type cLBV[5]
Astrometry
Radial velocity (Rv)−26.0[6] km/s
Proper motion (μ) RA: −1.01[1] mas/yr
Dec.: −4.01[1] mas/yr
Parallax (π)1.27 ± 0.25[1] mas
Distanceapprox. 2,600 ly
(approx. 800 pc)
Absolute magnitude (MV)−8.5[4]
Details
Mass36[4] M☉
Radius103[4] R☉
Luminosity (bolometric)850,000[4] L☉
Surface gravity (log g)1.7[4] cgs
Temperature17,200[4] K
Rotational velocity (v sin i)60[7] km/s
Age6.5 ± 0.1[8] Myr
Other designations
ζ1 Sco, CD−42 11633, CPD−42 7545, GC 22730, HD 152236, HIP 82671, HR 6262, PPM 322342, SAO 227375.[9]
Database references
SIMBADdata
ζ1 Scorpii alongside the brighter ζ2 Scorpii to the south of NGC 6231

The stellar wind from this supergiant is expelling matter from the star at the rate of 1.55 × 10−6 solar masses per year, or roughly the equivalent to the Sun's mass every 640,000 years.[4]

ζ1 Scorpii forms a naked eye double with ζ2 Scorpii, but the stars are merely coincidentally near in the line of sight from Earth. ζ2 is a mere 155 light years distant and much less luminous in real terms. ζ1 Scorpii can also be distinguished from ζ2, due to the latter's orange hue especially in long-exposure photographs.

ζ1 Scorpii is a candidate luminous blue variable (cLBV), a star with the luminosity and spectral appearance of an LBV, but one that has not yet shown the characteristic types of variability.[5] It has been classified as dormant or ex-S Doradus variable, an older name for LBVs.[11]

References
  1. van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Note: see VizieR catalogue I/311 Archived 2012-12-05 at Archive.today.
  2. Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series, 61: 387–405, Bibcode:1985A&AS...61..387K
  3. zet 1 Sco, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 20, 2009. (Quick look: Zet+1+Sco Archived 2012-03-07 at the Wayback Machine)
  4. Clark, J. S.; Najarro, F.; Negueruela, I.; Ritchie, B. W.; Urbaneja, M. A.; Howarth, I. D. (2012). "On the nature of the galactic early-B hypergiants". Astronomy & Astrophysics. 541: A145. arXiv:1202.3991. Bibcode:2012A&A...541A.145C. doi:10.1051/0004-6361/201117472.
  5. Nazé, Y.; Rauw, G.; Hutsemékers, D. (2012). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics. 538: A47. arXiv:1111.6375. Bibcode:2012A&A...538A..47N. doi:10.1051/0004-6361/201118040.
  6. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, University of Toronto: International Astronomical Union, 30: 57, Bibcode:1967IAUS...30...57E
  7. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B
  8. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
  9. HIP 82671 -- Emission-line Star, database entry, SIMBAD. Accessed on line November 20, 2009.
  10. Zeta-1 Sco Archived 2009-10-17 at the Wayback Machine, Stars, Jim Kaler. Accessed on line November 20, 2009.
  11. Van Genderen, A. M. (2001). "S Doradus variables in the Galaxy and the Magellanic Clouds". Astronomy and Astrophysics. 366 (2): 508. Bibcode:2001A&A...366..508V. doi:10.1051/0004-6361:20000022.
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