Zeta1 Scorpii

Zeta¹ Scorpii is a binary star in the constellation of Scorpius, composed by an B-type hypergiant star as the primary, and a secondary of which little is known. It has an apparent visual magnitude which varies between 4.66 and 4.86. It is a member of the Scorpius OB1 association, and potentially of the open star cluster NGC 6231, also known as the "Northern jewel box" cluster.

Characteristics

ζ¹ Scorpii's primary is a luminous blue variable according to its luminosity and spectral appearance, yet is has not shown the characteristic types of variability, hence is classified as a dormant LBV. It has around 36 times as massive as the Sun and is one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity between 1 and 1.6 million times that of the Sun and a radius around 160 times that of the Sun. The stellar wind from this supergiant is expelling matter from the star at the rate of per year, or roughly the equivalent to the Sun's mass every 640,000 years.
The secondary has been detected using interferometry, and its discovery was announced in 2021., it has an angular separation of along a position angle of. It is 6.3 magnitudes fainter than the primary.
File:NGC 6231 and ζ Sco AOFPK.jpg|thumb|left|upright|ζ¹ Scorpii alongside the brighter ζ² Scorpii to the south of NGC 6231
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 135 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.