Theta Aquarii (θ Aquarii, abbreviated Theta Aqr, θ Aqr), officially named Ancha /ˈæŋkə/ [7] (distinguish Ankaa, with the same pronunciation), is a star in the equatorial constellation of Aquarius. Visible to the naked eye at apparent magnitude 4.175, [2] it is located at a distance of around 187 light-years (57 parsecs ) from the Sun. [1] Since it is near the ecliptic it can be occulted by the Moon, or very rarely by planets.
θ Aquarii (Latinised to Theta Aquarii) is the star's Bayer designation.
It bore the traditional name Ancha; Medieval Latin for "the haunch". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [8] to catalogue and standardize proper names for stars. The WGSN approved the name Ancha for this star on 12 September 2016, and it is now so included in the List of IAU-approved Star Names. [7]
In Chinese, 泣 (Qì), meaning Weeping , refers to an asterism consisting of Theta Aquarii and Rho Aquarii. [9] Consequently, the Chinese name for Theta Aquarii itself is 泣二 (Qì èr, English: the Second Star of Weeping). [10] Possibly, the name Lei, meaning "tears (weeping)" in Chinese, derives from the Chinese name for this star. [11]
Ancha belongs to the spectral class G8 with a luminosity class of III–IV suggesting that, at an age of 437 [3] million years, this star is part way between the subgiant and giant stages of its evolution. Estimates of the star's mass range from 2.39 [5] to 2.78 [3] times the Sun's mass, with a radius of about 12 [4] times that of the Sun. It is radiating from 72 [4] to 83 [3] times as much luminosity as the Sun from its enlarged outer envelope at an effective temperature of 4,864 K. [4] At this heat, the star glows with the yellow hue of a G-type star. [12]
Kappa Aquarii is a probable binary star in the equatorial constellation of Aquarius. This system is visible to the naked eye, but it is faint at an apparent magnitude of 5.03. Based upon parallax measurements made during the Hipparcos mission, it is around 214 light-years from the Sun.
Theta Scorpii is a binary star in the southern zodiac constellation of Scorpius. The apparent visual magnitude of this star is +1.87, making it readily visible to the naked eye and one of the brightest stars in the night sky. It is sufficiently near that the distance can be measured directly using the parallax technique and such measurements obtained during the Hipparcos mission yield an estimate of approximately 329 light-years from the Sun.
Theta Centauri or θ Centauri, officially named Menkent, is a single star in the southern constellation of Centaurus, the centaur. With an apparent visual magnitude of +2.06, it is the fourth-brightest member of the constellation. Based on parallax measurements obtained during the Hipparcos mission, it is about 58.8 light-years distant from the Sun. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.73 arcsecond/yr. This suggests that Menkent may have originated in the outer disk of the Milky Way and is merely passing through the solar neighborhood.
Beta Pegasi, formally named Scheat, is a red giant star and the second-brightest star in the constellation of Pegasus. It forms the upper right corner of the Great Square of Pegasus, a prominent rectangular asterism.
Delta Aquarii, officially named Skat, is the third-brightest star in the constellation of Aquarius. The apparent visual magnitude is 3.3, which can be seen with the naked eye. The distance to this star is about 113 light-years based upon parallax measurements, and it has a close companion.
Alpha Aquarii, officially named Sadalmelik, is a single yellow supergiant star in the constellation of Aquarius. The apparent visual magnitude of 2.94 makes this the second-brightest star in Aquarius. Based upon parallax measurements made by the Gaia spacecraft, it is located at a distance of roughly 690 light-years from the Sun. It is drifting further away from the Sun with a radial velocity of 7.5 km/s.
Beta Aquarii is a single yellow supergiant star in the constellation of Aquarius. It has the official name Sadalsuud and the Bayer designation β Aquarii, abbreviated Beta Aqr or β Aqr. Based upon parallax measurements obtained during the Hipparcos mission, this component is located at a distance of approximately 540 light years (165 parsecs) from the Sun. It is drifting further away with a radial velocity of 6.5 km/s. The star serves as an IAU radial velocity standard.
Epsilon Aquarii, Latinized from ε Aquarii, is a binary star in the equatorial zodiac constellation of Aquarius, located near the western constellation border with Capricornus. It has the proper name Albali, now formally recognized by the IAU. It is visible to the naked eye with an apparent visual magnitude of 3.77, and has an absolute magnitude of −0.46. Based upon parallax measurements taken by the Gaia spacecraft, it is located at a distance of approximately 244 light-years (75 pc) from Earth. The star is drifting closer with a radial velocity of −20 km/s.
Xi Aquarii is a binary star system in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.7. Based upon parallax measurements made during the Hipparcos mission, this system lies at a distance of around 179 light-years from the Sun.
Theta Serpentis is a triple star system in the constellation of Serpens.
Kappa Virginis, officially named Kang, is a solitary star in the zodiac constellation of Virgo. It has an apparent visual magnitude of 4.18, which is sufficiently bright to be seen with the naked eye. Based upon stellar parallax measurements, the distance to this star is about 255 light-years.
91 Aquarii is the Flamsteed designation for a triple star system in the equatorial constellation of Aquarius. It also bears the Bayer designation Psi1 Aquarii. It is visible to the naked eye with an apparent visual magnitude of +4.248. Parallax measurements yield an estimated distance of around 150 light-years from Earth. An extrasolar planet is known to orbit the main star.
Nu Aquarii is the Bayer designation for a star in the equatorial constellation of Aquarius.
Theta Aurigae is a binary star in the constellation of Auriga. Based upon parallax measurements, the distance to this system is about 166 light-years.
104 Aquarii (abbreviated 104 Aqr) is a star in the equatorial constellation of Aquarius. 104 Aquarii is the Flamsteed designation, although it also bears the Bayer designation A2 Aquarii. Based on an annual parallax shift of only 3.89 ± 0.25 milliarcseconds, the distance to this star is about 840 light-years (260 parsecs). At that range, the brightness of the star in the V-band is reduced by 0.10 magnitudes as a result of extinction caused by intervening gas and dust.
25 Aquarii is a single star in the equatorial constellation of Aquarius. 25 Aquarii is the modern Flamsteed designation; in the past it held the designation 6 Pegasi. It also bears the Bayer designation of d Aquarii. It is located near the border with the modern Pegasus constellation. Although faint at an apparent visual magnitude of +5.09, it is bright enough to be viewed from suburban skies. Based upon an annual parallax shift of 0.01440 arcseconds, it is located at a distance of around 226 light-years from Earth. The visual magnitude of the star is diminished by 0.09 from extinction caused by intervening gas and dust.
60 Aquarii is a star located 375 light years away from the Sun in the equatorial constellation of Aquarius. 60 Aquarii is its Flamsteed designation. It is visible to the naked eye as a dim, yellow-hued star with an apparent visual magnitude of 5.89. The star is moving closer to the Earth with a heliocentric radial velocity of –8 km/s.
θ Pegasi, Latinized as Theta Pegasi, is a single star in the equatorial constellation of Pegasus, lying about 7.5 degrees southwest of Enif. It has the traditional name Biham, and the Flamsteed designation 26 Pegasi. This object is visible to the naked eye as a white-hued point of light with an apparent visual magnitude of +3.52. The system is located 92 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −8 km/s.
Theta Columbae, also named Elkurud, is a solitary star in the southern constellation of Columba. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.02. Based upon parallax measurements taken during the Hipparcos mission, it is roughly 720 light-years distant from the Sun. At its present distance, the visual magnitude of the star is reduced by an interstellar extinction factor of 0.11. It is currently moving away from the Sun with a radial velocity of 45.3 km/s. The star made its closest approach about 4.7 million years ago when it underwent perihelion passage at a distance of 10.9 ly (3.33 pc).
Upsilon1 Hydrae, also named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12. Based upon an annual parallax shift of 12.36 mas as seen from Earth, it is located about 264 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −14.34 km/s. In 2005 it was announced that it had a substellar companion.