| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h24m 13.78599s[1] |
| Declination | +39° 30′ 26.0473″[1] |
| Apparent magnitude (V) | 5.11[2] |
| Characteristics | |
| Evolutionary stage | subgiant[3] |
| Spectral type | A0 IV[4] |
| U−B color index | +0.07[5] |
| B−V color index | +0.047±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | −24.0±4.2[2] km/s |
| Proper motion (μ) | RA: −21.825±0.260[1] mas/yr Dec.: −4.460±0.288[1] mas/yr |
| Parallax (π) | 7.9161 ± 0.1438 mas[1] |
| Distance | 412 ± 7 ly (126 ± 2 pc) |
| Absolute magnitude (MV) | –0.53[2] |
| Details | |
| Mass | 3.04±0.04[3] M☉ |
| Radius | 4.5[6] R☉ |
| Luminosity | 200+23 −10[3] L☉ |
| Temperature | 9,016+167 −165[3] K |
| Rotational velocity (v sin i) | 165[3] km/s |
| Other designations | |
μ Lyr, 2 Lyrae, BD+39°3410, HD 169702, HIP 90191, HR 6903, SAO 66943[7] | |
| Database references | |
| SIMBAD | data |
μ Lyrae, Latinized as Mu Lyrae, is a solitary[8] star in the northern constellation Lyra. It has the traditional name Alathfar /əˈlæθfɑːr/, from the Arabic الأظفار al-ʼaẓfār "the talons (of the swooping eagle)", a name it shares with Eta Lyrae[9] (though the latter is spelled "Aladfar" by the IAU).[10] This white-hued object is visible to the naked eye as faint point of light with an apparent visual magnitude of 5.11.[2] It is located approximately 412 light years distant from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −24 km/s.[2]
This object has evolved off the main sequence,[3] becoming a subgiant with a stellar classification of A0 IV.[4] It has a fairly high rate of spin, showing a projected rotational velocity of 165 km/s.[3] This is giving the star an equatorial bulge that is an estimated 17% larger than the polar radius.[11] The star has three[3] times the mass of the Sun and about 4.5[6] times the Sun's radius. It is radiating 200[3] times the Sun's luminosity from its photosphere at an effective temperature of 9,016 K.[3]
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