3 Equulei
K-type giant star in the constellation Equuleus
From Wikipedia, the free encyclopedia
3 Equulei is a single[3] star located in the small northern constellation of Equuleus. It is faintly visible to the naked eye at an apparent visual magnitude of 5.6.[2] Based upon an annual parallax shift of 2.7 mas, 3 Equulei is roughly 1,220 light-years (370 parsecs) distant from Earth, give or take a 40 light-year margin of error. At that distance, the apparent brightness of the star is diminished by 0.15 in visual magnitude because of extinction from interstellar gas and dust.[4]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Equuleus |
| Right ascension | 21h 04m 34.65162s[1] |
| Declination | +05° 30′ 10.3117″[1] |
| Apparent magnitude (V) | 5.593[2] |
| Characteristics | |
| Evolutionary stage | red giant branch[1] |
| Spectral type | K5 III[3] |
| U−B color index | +1.934[2] |
| B−V color index | +1.651[2] |
| Astrometry | |
| Radial velocity (Rv) | −15.26±0.2[4] km/s |
| Proper motion (μ) | RA: +13.115[1] mas/yr Dec.: +0.752[1] mas/yr |
| Parallax (π) | 2.6635±0.0940 mas[1] |
| Distance | 1,220 ± 40 ly (380 ± 10 pc) |
| Absolute magnitude (MV) | −1.02[5] |
| Details | |
| Mass | 7.2[1] M☉ |
| Radius | 116[6] R☉ |
| Luminosity | 2,581[1] L☉ |
| Surface gravity (log g) | 1.06[1] cgs |
| Temperature | 4,029[6] K |
| Rotational velocity (v sin i) | 4.6[7] km/s |
| Other designations | |
| ζ Equ, 3 Equ, BD+04°4606, HD 200644, HIP 104031, HR 8066, SAO 126518[8] | |
| Database references | |
| SIMBAD | data |
3 Equulei has been referred to in some sources as ζ (Zeta) Equulei, although it was not given that designation by Bayer.[9]
Properties
3 Equulei is an evolved giant star with a stellar classification of K5 III.[3] The measured angular diameter of this star, after correction for limb darkening, is 2.44±0.03 mas.[10] At the estimated distance of 1,220 light-years, this yields a physical size of about 100 times the radius of the Sun.[11] It is radiating an estimated 2,581 times the luminosity of the Sun[1] from this expanded outer envelope at an effective temperature of 4,029 K.[6] At this temperature, it shines with the orange-hued glow of a K-type star.[12]
