Zeta1 Scorpii

ζ¹ Scorpii

Location of ζ^1 Scorpii (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Scorpius
Right ascension	16^h 53^m 59.72650^s[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	SDOR:[3]
Astrometry
Radial velocity (Rv)	−26.0[5] 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
Distance	approx. 2,600 ly (approx. 800 pc)
Absolute magnitude (MV)	−8.5[4]
Details
Mass	36[4] M☉
Radius	103[4] R☉
Luminosity (bolometric)	850,000[4] L☉
Surface gravity (log g)	1.7[4] cgs
Temperature	17,200[4] K
Rotational velocity (v sin i)	60[6] km/s
Age	6.5 ± 0.1[7] Myr
Other designations
ζ^1 Sco, Zeta^1 Scorpii, Zeta^1 Sco, CD−42 11633, CPD−42 7545, GC 22730, HD 152236, HIP 82671, HR 6262, PPM 322342, SAO 227375.[8]
Database references
SIMBAD	data

Zeta¹ Scorpii (Zeta¹ Sco, ζ¹ Scorpii, ζ¹ Sco) is a B-type hypergiant star in the constellation of Scorpius.^[8] It has an apparent visual magnitude which varies between 4.66 and 4.86.^[3] It is a member of the Scorpius OB1 association,^[9] and the open star cluster NGC 6231, also known as the "northern jewel box" cluster. It is also one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity of nearly a million times the Sun's.

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.

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.
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, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 20, 2009. (Quick look: Zet+1+Sco)
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. 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
6. 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
7. 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
8. HIP 82671 -- Emission-line Star, database entry, SIMBAD. Accessed on line November 20, 2009.
9. Zeta-1 Sco, Stars, Jim Kaler. Accessed on line November 20, 2009.