Zeta¹ Scorpii (Zeta¹ Sco, ζ¹ Scorpii, ζ¹ Sco) is a B-type

hypergiant A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term ''hypergiant'' is defined as luminosity class 0 (zero) in the MK ...

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the Gre ...

. It has an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

which varies between 4.66 and 4.86. It is a member of the Scorpius OB1 association, and the

open star cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

NGC 6231 NGC 6231 (also known as Caldwell 76) is an open cluster in the southern sky located half a degrees north of Zeta Scorpii. NGC 6231 is part of a swath of young, bluish stars in the constellation Scorpius known as the Scorpius OB1 association. The ...

, 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 This is a list of stars arranged by their absolute magnitude – their intrinsic stellar luminosity. This cannot be observed directly, so instead must be calculated from the apparent magnitude (the brightness as seen from Earth), the distance t ...

known in the Galaxy, with an estimated

bolometric luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a s ...

of around 850,000 times that of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

and a radius 103 times that of the Sun. The

stellar wind A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric. D ...

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. 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 year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s 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 Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Larg ...

(cLBV), a star with the luminosity and spectral appearance of an LBV, but one that has not yet shown the characteristic types of variability. It has been classified as dormant or ex-

S Doradus S Doradus (also known as S Dor) is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, located roughly 160,000 light-years away. The star is a luminous blue variable, and one of the ...

variable, an older name for LBVs.

References

{{Stars of Scorpius Scorpius (constellation) B-type hypergiants 082671 Scorpii, Zeta1 152236 Emission-line stars 6262 CD-42 11633