Phi Aquarii
Star in the constellation Aquarius
From Wikipedia, the free encyclopedia
Phi Aquarii is a binary star[8] system in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from φ Aquarii, and abbreviated Phi Aqr or φ Aqr. This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of +4.223.[2] Parallax measurements indicate its distance from Earth is approximately 227 light-years (70 pc).[1] It is drifting further away with a radial velocity of +2.5 km/s.[4] The system is positioned 1.05 degrees south of the ecliptic so it is subject to lunar occultations.[9]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 23h 14m 19.358s[1] |
| Declination | −06° 02′ 56.42″[1] |
| Apparent magnitude (V) | +4.223[2] |
| Characteristics | |
| Spectral type | M1.5 III[3] |
| U−B color index | +1.897[2] |
| B−V color index | +1.563[2] |
| Astrometry | |
| Radial velocity (Rv) | +2.48±0.32[4] km/s |
| Proper motion (μ) | RA: +36.575 mas/yr[1] Dec.: −195.441 mas/yr[1] |
| Parallax (π) | 14.3482±0.2594 mas[1] |
| Distance | 227 ± 4 ly (70 ± 1 pc) |
| Absolute magnitude (MV) | 0.30±0.120[5] |
| Details | |
| A | |
| Mass | 1.00±0.03[6] M☉ |
| Radius | 34.77+1.83 −2.04[6] R☉ |
| Luminosity | 207.7±25.2[6] L☉ |
| Surface gravity (log g) | 1.5[4] cgs |
| Temperature | 3,715±48[6] K |
| Rotational velocity (v sin i) | 6.7[4] km/s |
| Age | 10.97±0.83[6] Gyr |
| Other designations | |
| φ Aqr, 90 Aquarii, BD−06°6170, FK5 1607, GC 32346, HD 219215, HIP 114724, HR 8834, SAO 146585, PPM 207311[7] | |
| Database references | |
| SIMBAD | data |
This is a spectroscopic binary star system with an estimated period of 2,500 days (6.8 yr).[10] The primary component is an aging red giant star with a stellar classification of M1.5 III.[3] At an estimated age of 11 billion years,[6] it has exhausted the supply of hydrogen at its core and evolved away from the main sequence. The star has the same mass as the Sun,[6] but has expanded to 35 times the Sun's girth.[6] It is radiating 208 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,715 K,[6] giving it the reddish hue of an M-type star.[11]
On 6 September 2019, it had a close conjunction (geocentric separation <1') with Neptune.[12] : 167