Phi Eridani
Blue-hued star in the constellation Eridanus
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φ Eridani (Latinised as Phi Eridani) is a star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.55.[2] The distance to this star, as determined using the parallax method, is around 154 light-years.[1]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 02h 16m 30.58563s[1] |
| Declination | −51° 30′ 43.7955″[1] |
| Apparent magnitude (V) | 3.55[2] |
| Characteristics | |
| Spectral type | B8IV-V[3] |
| U−B color index | −0.38[2] |
| B−V color index | −0.12[2] |
| Astrometry | |
| Radial velocity (Rv) | 10.40[4] km/s |
| Proper motion (μ) | RA: +91.03[1] mas/yr Dec.: −22.23[1] mas/yr |
| Parallax (π) | 21.22±0.12 mas[1] |
| Distance | 153.7 ± 0.9 ly (47.1 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.183±0.027[5] |
| Details | |
| Mass | 3.55[6] M☉ |
| Radius | 2.422[7] R☉ |
| Luminosity | 135[7] L☉ |
| Surface gravity (log g) | 4.21±0.14[6] cgs |
| Temperature | 12,650[7] K |
| Rotation | 0.343705[8] d |
| Rotational velocity (v sin i) | 250[9] km/s |
| Age | 44[6] Myr |
| Other designations | |
| φ Eri, CPD−52°285, FK5 82, HD 14228, HIP 10602, HR 674, SAO 232696[10] | |
| Database references | |
| SIMBAD | data |
This is a B-type star with a stellar classification of B8IV-V,[3] suggesting it shows traits of a main-sequence star and a subgiant. It is spinning rapidly with a projected rotational velocity of 250 km/s. This rotation is giving the star an oblate shape with an equator that is 17% larger than the polar radius.[9] It has 3.55 times the mass of the Sun and radiates 135 times the solar luminosity from its outer atmosphere at an effective temperature of about 12,650 K.[6][7]
Phi Eridani may form a wide binary star system with a 9th-magnitude star at lies an angular separation of 86″. This companion is a G-type main-sequence star with a stellar classification of G2V.[11] It may also have a physical association with the naked-eye star Eta Horologii.[12] It is a member of the Tucana-Horologium association, a 45(±4)-Myr-old group of stars that share a common motion through space.[5]