7 Aquarii, abbreviated 7 Aqr, is a binary star[3] system in the zodiac constellation of Aquarius. 7 Aquarii is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 5.5;[2] the brighter component is baseline magnitude 5.62 while the faint secondary is magnitude 11.4.[3] As of 2002, the pair had an angular separation of 2.10″ along a position angle of 165°.[10] The distance to this system, based upon an annual parallax shift of 4.9 mas,[1] is around 660 light years. It is moving closer to the Earth with a heliocentric radial velocity of −32 km/s.[7]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 20h 56m 54.02626s[1] |
Declination | −09° 41′ 51.1610″[1] |
Apparent magnitude (V) | 5.499[2] (5.62 + 11.4)[3] |
Characteristics | |
Spectral type | K4 III[4] |
B−V color index | +1.474±0.006[5] |
Variable type | Suspected[6] |
Astrometry | |
Radial velocity (Rv) | −32.4±1.6[7] km/s |
Proper motion (μ) | RA: −5.577[1] mas/yr Dec.: −10.245[1] mas/yr |
Parallax (π) | 4.9495 ± 0.1309 mas[1] |
Distance | 660 ± 20 ly (202 ± 5 pc) |
Absolute magnitude (MV) | −0.61[5] |
Details | |
Radius | 46[8] R☉ |
Luminosity | 403.66[5] L☉ |
Surface gravity (log g) | 1.650[2] cgs |
Temperature | 3,990[2] K |
Metallicity [Fe/H] | −0.17[2] dex |
Other designations | |
Database references | |
SIMBAD | data |
The primary component is an aging giant star with a stellar classification of K4 III.[4] It is a suspected variable star of unknown type with a maximum magnitude of 5.48.[6] The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 2.14±0.02 mas,[11] which, at its estimated distance, equates to a physical radius of about 46 times the radius of the Sun.[8] The star is radiating 404[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,990 K.[2]