25 Aquarii
Single, K-type star in the constellation Aquarius
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25 Aquarii (abbreviated 25 Aqr) is a single[5] star in the equatorial constellation of Aquarius. 25 Aquarii is the modern Flamsteed designation; in the past it held the designation 6 Pegasi.[9] 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,[3] it is bright enough to be viewed from suburban skies. Based upon an annual parallax shift of 0.0132 arcseconds, it is located at a distance of around 247 light-years (76 parsecs) from Earth. The visual magnitude of the star is diminished by 0.09 from extinction caused by intervening gas and dust.[10]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius[1] |
| Right ascension | 21h 39m 33.26719s[2] |
| Declination | +02° 14′ 36.8193″[2] |
| Apparent magnitude (V) | +5.09[3] |
| Characteristics | |
| Evolutionary stage | red clump[4] |
| Spectral type | K0 III[5] |
| U−B color index | +0.90[3] |
| B−V color index | +1.032[6] |
| Astrometry | |
| Radial velocity (Rv) | −34.63±0.11[6] km/s |
| Proper motion (μ) | RA: −30.179[2] mas/yr Dec.: −83.636[2] mas/yr |
| Parallax (π) | 13.2155±0.0892 mas[2] |
| Distance | 247 ± 2 ly (75.7 ± 0.5 pc) |
| Absolute magnitude (MV) | +0.768[7] |
| Details | |
| Mass | 3.0[2] M☉ |
| Radius | 11[6] R☉ |
| Luminosity | 54[6] L☉ |
| Surface gravity (log g) | 2.67[2] cgs |
| Temperature | 4,721[6] K |
| Metallicity [Fe/H] | −0.17[6] dex |
| Rotational velocity (v sin i) | 2.5[6] km/s |
| Age | 377[2] Myr |
| Other designations | |
| d Aquarii, 25 Aqr, 6 Pegasi, BD+01 4517, FK5 3729, HD 206067, HIP 106944, HR 8277, SAO 126965[8] | |
| Database references | |
| SIMBAD | data |
The spectrum of this star matches a stellar classification of K0 III,[5] with the luminosity class of III indicating that this is a giant star that has evolved away from the main sequence after exhausting the supply of hydrogen at its core. It belongs to a population known as clump giants and hence is generating energy through the nuclear fusion of helium at the core.[4] The outer envelope has expanded to 11 times the radius of the Sun and it is radiating 54 times the Sun's luminosity.[6] This energy is being emitted from the stellar atmosphere at an effective temperature of 4,721 K,[6] causing it to glow with the orange hue of a K-type star.[11]