Epsilon Normae
Triple star system in the constellation Norma
From Wikipedia, the free encyclopedia
Epsilon Normae, Latinised from ε Normae, is a blue-white hued triple star[5] system in the southern constellation of Norma. It has an apparent visual magnitude of 4.47,[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 6.15 mas as seen from Earth,[1] the system is located around 530 light years distant from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.21 due to interstellar dust.[7]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Norma |
| A | |
| Right ascension | 16h 27m 11.03611s[1] |
| Declination | −47° 33′ 17.2226″[1] |
| Apparent magnitude (V) | 4.47[2] |
| B | |
| Right ascension | 16h 27m 10.06643s[3] |
| Declination | −47° 32′ 56.6763″[3] |
| Apparent magnitude (V) | 6.13[4] |
| Characteristics | |
| Spectral type | B4 V + B4 V + B9 V[5] |
| U−B color index | −0.54[2] |
| B−V color index | −0.07[2] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −12.5±2.7[6] km/s |
| Proper motion (μ) | RA: −13.68±0.27[1] mas/yr Dec.: −19.89±0.20[1] mas/yr |
| Parallax (π) | 6.15±0.28 mas[1] |
| Distance | 530 ± 20 ly (163 ± 7 pc) |
| Absolute magnitude (MV) | +0.06[7] |
| B | |
| Radial velocity (Rv) | −6.67±0.83[3] km/s |
| Proper motion (μ) | RA: −10.393[3] mas/yr Dec.: −20.277[3] mas/yr |
| Parallax (π) | 5.4467±0.0299 mas[3] |
| Distance | 599 ± 3 ly (184 ± 1 pc) |
| Orbit[8] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 3.2617 d |
| Eccentricity (e) | 0.13 |
| Periastron epoch (T) | 2438825.9310 JD |
| Argument of periastron (ω) (secondary) | 271.5° |
| Semi-amplitude (K1) (primary) | 122.5 km/s |
| Semi-amplitude (K2) (secondary) | 132.9 km/s |
| Details | |
| Aa | |
| Mass | 7.7[9] M☉ |
| Ab | |
| Mass | 4.5[9] M☉ |
| B | |
| Mass | 2.3[9] M☉ |
| Radius | 2.4[3] R☉ |
| Luminosity | 74[3] L☉ |
| Surface gravity (log g) | 4.00[3] cgs |
| Temperature | 11,104[3] K |
| Other designations | |
| ε Nor, CD−47°10765, HD 147971, HIP 80582, HR 6115, SAO 226773, WDS J16272-4733A[10] | |
| B: HD 147970, HIP 80579[11] | |
| Database references | |
| SIMBAD | data |
| B | |
The inner pair form a double-lined spectroscopic binary[12] system with an orbital period of 3.26 days and an eccentricity of 0.13.[8] Both stars appear to be similar B-type main-sequence stars with stellar classifications of B4 V.[5]
The third component, at an angular separation of 22.8 arc seconds from the inner pair, is HD 147970. It is most likely is a smaller B-type main sequence star of spectral type B9V.[5]