Tau2 Aquarii
Star in the constellation Aquarius
From Wikipedia, the free encyclopedia
Tau2 Aquarii is a solitary[11] star in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from τ2 Aquarii, and abbreviated Tau2 Aqr or τ2 Aqr. This star is visible to the naked eye with an apparent visual magnitude of +4.0.[2] Because the star lies near the ecliptic it is subject to occultations by the Moon.[12] The star is located at a distance of approximately 326 light-years (100 pc) from the Sun based on parallax.[1] It is drifting further away with a radial velocity of about +1.1 km/s.[6]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 49m 35.501s[1] |
| Declination | −13° 35′ 33.46″[1] |
| Apparent magnitude (V) | +4.042[2] (3.98 to 4.04)[3] |
| Characteristics | |
| Spectral type | K5 III[4] or M0 III[5] |
| U−B color index | +1.948[2] |
| B−V color index | +1.566[2] |
| Variable type | Suspected[3] |
| Astrometry | |
| Radial velocity (Rv) | +1.1±0.8[6] km/s |
| Proper motion (μ) | RA: −13.386 mas/yr[1] Dec.: −38.609 mas/yr[1] |
| Parallax (π) | 10.0171±0.1734 mas[1] |
| Distance | 326 ± 6 ly (100 ± 2 pc) |
| Absolute magnitude (MV) | −1.28[7] |
| Details | |
| Radius | 51.5+4.6 −5.5[8] R☉ |
| Luminosity | 614±27[8] L☉ |
| Surface gravity (log g) | 1.63[9] cgs |
| Temperature | 4,007+232 −166[8] K |
| Other designations | |
| τ2 Aquarii, τ2 Aqr, 71 Aquarii, NSV 14329, BD−14°6354, FK5 861, GC 31836, HD 216032, HIP 112716, HR 8679, SAO 165321, PPM 240808, WDS J22496-1336A[10] | |
| Database references | |
| SIMBAD | data |
This is an orange-hued[13] red giant star with a stellar classification of K5 III.[4] After exhausting the supply of hydrogen at its core, the aging star cooled and expanded off the main sequence. It now has 52 times the radius of the Sun and is radiating 614 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,007 K.[8] This is a suspected variable star with a brightness that has been measured ranging from visual magnitude 3.98 down to 4.04.[3]
A magnitude 9.94 visual companion to this star was reported by W. Herschel in 1782, and it has the modern discovery code 'H 6 97'. As of 2010, it was located at a wide angular separation of 132.40″ from the brighter star along a position angle of 297°.[14]