Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 22h 37m 45.38049s [1] |
Declination | −04° 13′ 40.9939″ [1] |
Apparent magnitude (V) | 5.03 [2] |
Characteristics | |
Spectral type | K2 III [3] |
U−B color index | +1.16 [2] |
B−V color index | +1.142 [4] |
Astrometry | |
Radial velocity (Rv) | +7.31 ± 0.16 [4] km/s |
Proper motion (μ) |
RA: −69.23
[1]
mas/
yr Dec.: −119.67 [1] mas/ yr |
Parallax (π) | 15.25 ± 0.21 mas [1] |
Distance | 214 ± 3
ly (65.6 ± 0.9 pc) |
Absolute magnitude (MV) | +0.96 [5] |
Details | |
Radius | 13 [4] R☉ |
Luminosity | 60 [4] L☉ |
Surface gravity (log g) | 2.5 [4] cgs |
Temperature | 4,581 [4] K |
Metallicity [Fe/H] | +0.14 [4] dex |
Rotational velocity (v sin i) | 3.8 [4] km/s |
Other designations | |
Database references | |
SIMBAD | data |
Kappa Aquarii (κ Aquarii, abbreviated Kappa Aqr, κ Aqr) 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. [2] Based upon parallax measurements made during the Hipparcos mission, it is around 214 light-years (66 parsecs) from the Sun. [2]
The two components are designated Kappa Aquarii A (formally named Situla /ˈsɪtjuːlə/, the traditional name for the system) [7] and B.
κ Aquarii ( Latinised to Kappa Aquarii) is the system's Bayer designation. The designations of the two components as Kappa Aquarii A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). [8]
It bore the traditional name Situla, a Latin word meaning "bucket" or "water jar". [9] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [10] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. [11] It approved the name Situla for the component Kappa Aquarii A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. [7]
In Chinese, 虛梁 (Xū Liáng), meaning Temple, refers to an asterism consisting of Kappa Aquarii, 44 Aquarii, 51 Aquarii and HD 216718. [12] Consequently, the Chinese name for Kappa Aquarii itself is 虛梁三 (Xū Liáng sān, English: the Third Star of Temple). [13] From this Chinese name, the name Heu Leang has appeared, meaning "the empty bridge". [9]
USS Situla (AK-140) was a United States Navy Crater-class cargo ship named after the star.
Kappa Aquarii is most probably a wide binary star system. [14] The brighter component is a giant star with a stellar classification of K2 III. [3] It has exhausted the supply of hydrogen at its core and has expanded to 13 [4] times the radius of the Sun. It is radiating 60 [4] times the Sun's luminosity from its outer envelope at an effective temperature of 4,581 K, [4] giving it the orange-hued glow of a K-type star. [15]
The fainter companion star is located at an angular separation of 98.3 arcseconds and has an apparent magnitude of 8.8. [15]
Endymion, an 1818 poem by John Keats, describes the star in its form as a water urn thus:
Crystalline brother of the belt of heaven,
Aquarius! to whom King Jove has given
Two liquid pulse streams 'stead of feather'd wings,
Two fan-like fountains, — thine illuminings. [16]