Zeta Scorpii

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Zeta Scorpii
Observational Data
Designation ζ Sco
ζ Scorpii
HD 152236
Right ascension 16h 53m 59.7270s[1][2]
Declination -42° 21′ 43.3137″[1][2]
Constellation Scorpius
Type of object Hypergiant star
Magnitude Apparent Mag: 4.705[3]
Absolute Mag: -8.5
Distance from Earth 2,600 ly[3]
Radial velocity -26.00±0.8 km/s[1][4]
Proper motion RA: 0.009 mas/yr[1][2]
Dec.: -2.939 mas/yr[1][2]
Parallax 0.7131±0.2420 mas[1][2]

Zeta Scorpii (ζ Sco, ζ Scorpii, HD 152236) is a Bayer designation shared by two stars in the constellation of Scorpius.[3]Zeta-1 Scorpii is a hypergiant star whereas Zeta-2 Scorpii is a giant star. Although these stars appear only 7 arcminutes apart in the night sky, they only form a visual binary, meaning they only appear to be close to one another as they lie along the same line of sight. In fact, Zeta-1 Scorpii is 40 times further away than Zeta-2 Scorpii.[5] The star Zeta-1 Scorpii is one of the most luminous stars known, thought to be nearly a million times brighter than the Sun. This article discusses Zeta-1 Scorpii unless explicitly said.

Properties and Structure

Zeta-1 Scorpii (sometimes written as ζ1 Scorpii) is a B type hypergiant star and part of the open cluster NGC 6231.[6] It is also a candidate luminous blue variable star. The star's surface is incredibly hot with a temperature of 21,000 kelvin.[5] Unsurprisingly for a hypergiant star, it it truly massive; it is thought to have a mass of 36 solar masses though some sources place it at 60) and radius 103 times that of the Sun.[7][5][8] This large temperature and size means the star's luminosity is 850,000 times that of the Sun.[8] Large dust clouds situated in between Zeta-1 Scorpii and Earth attenuate its great luminosity so it only appears as a fourth magnitude star.[6] These are also thought to change the color to be a dull yellow.

The star is shedding large amounts of material in the form of a stellar wind. It is estimated at around 1.55×10−6 of a solar mass each and every year.[8]

Zeta-2 Scorpii

Zeta-2 Scorpii is a K type giant star lying closer than Zeta-1 Scorpii at only 151 light years.[3] It is smaller than Zeta-1 Scorpii but is brighter with a magnitude that varies between 3.59 and 3.65. This corresponds to an absolute magnitude of around 0.3. It is smaller with a mass of 1.19 solar masses and a radius 21 times larger than the Sun.[9]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 HD 152236. Simbad Astronomical Database. simbad.u-strasbg.fr. Retrieved on 2019-08-30.
  2. 2.0 2.1 2.2 2.3 2.4 Gaia Colaboration. VizieR Online Data Catalog: Gaia DR2 (Gaia Collaboration, 2018). (2018). VizieR Online Data Catalog. bibcode: 2018yCat.1345....0G
  3. 3.0 3.1 3.2 3.3 Scorpius Constellation. Retrieved on 2019-08-30.
  4. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759-771. doi:10.1134/S1063773706110065. Bibcode2006AstL...32..759G.  arXiv:1606.08053
  5. 5.0 5.1 5.2 Jim Kaler. ZETA-1 SCO. Stars. stars.astro.illinois.edu. Retrieved on 2019-08-30.
  6. 6.0 6.1 Zeta1 Scorpii. Retrieved on 2019-08-30.
  7. Clark, J. S.; Najarro, F.; Negueruela, I. et al. (2010). "On the nature of the galactic early-B hypergiants". Astronomy & Astrophysics 541 (A145). doi:10.1051/0004-6361/201117472. Bibcode2012A&A...541A.145C.  arXiv:1202.3991
  8. 8.0 8.1 8.2 Nazé, Y.; Rauw, G.; Hutsemékers, D. (2010). "The first X-ray survey of Galactic luminous blue variables". Astronomy & Astrophysics 538. doi:10.1051/0004-6361/201118040. Bibcode2012A&A...538A..47N.  arXiv:1111.6375
  9. da Silva, L.; Girardi, L.; Pasquini, L. et al. (2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics 458 (2): 609–623. doi:10.1051/0004-6361:20065105. Bibcode2006A&A...458..609D.  arXiv:astro-ph/0608160