AH Scorpii (abbreviated to AH Sco) is a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) and a stellar classification K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelg ...

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

located in the constellation

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 whose recognition pred ...

. It is one of the largest stars known by radius and is also one of the most luminous red supergiant stars in the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

Distance

Prior to the 21st century, the distance of AH Scorpii was considered to be uncertain, between about 1.5 and .

VLBI Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or in space. T ...

measurements of the masers have provided an accurate distance of based on observation of SiO, H₂O, and OH

masers A maser is a device that produces coherent electromagnetic waves ( microwaves), through amplification by stimulated emission. The term is an acronym for microwave amplification by stimulated emission of radiation. Nikolay Basov, Alexander Pro ...

in its oxygen-rich circumstellar material. The masers were observed to be approaching the star at 13 km/s, indicating overall contraction at around phase 0.55 of the visual variations.

Gaia Data Release 3 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, espec ...

includes a parallax of , corresponding to a distance of about .

Characteristics

AH Scorpii is a dust-enshrouded red supergiant and is classified as a

semiregular variable star In astronomy, a semiregular variable star, a type of variable star, is a giant or supergiant of intermediate and late (cooler) spectral type. It shows considerable periodicity in its light changes, accompanied or sometimes interrupted by various i ...

with a main period of 714 days. The total visual magnitude range is 6.5 - 9.6. No long secondary periods have been detected. Modelling of AH Scorpii near maximum light has determined an effective temperature of and a luminosity of . A radius of was determined from an

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular separation (in units of angle) describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the ''visual an ...

of and the given distance of . Its angular diameter was re-measured at in 2023.

References

{{Stars of Scorpius Semiregular variable stars Scorpius Scorpii, AH M-type supergiants 084071 155161 J17111702-3219308 CD-32 12429 TIC objects Population I stars

Distance

Characteristics

See also

References