Eta Lupi
Probable triple star system in the constellation of Lupus
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η Lupi, often Latinised as Eta Lupi, is a probable triple star[4][12] system in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 3.41.[2] Based upon an annual parallax shift of 27.80[1] mas as seen from Earth, it is located around 136 parsecs (440 ly) distant from the Sun. It is a member of the Upper Centaurus–Lupus subgroup of the nearby Sco OB2 association.[13]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Lupus |
| Right ascension | 16h 00m 07.32786s[1] |
| Declination | −38° 23′ 48.1513″[1] |
| Apparent magnitude (V) | 3.41[2] (3.37 + 7.50 + 10.85)[3] |
| Characteristics | |
| Spectral type | B2 IV + A5 Vp + F5 V[4] |
| U−B color index | −0.83[2] |
| B−V color index | −0.22[2] |
| Astrometry | |
| Radial velocity (Rv) | +1.00±3.80[5] km/s |
| Proper motion (μ) | RA: −16.96[1] mas/yr Dec.: −27.83[1] mas/yr |
| Parallax (π) | 7.38±0.18 mas[1] |
| Distance | 440 ± 10 ly (136 ± 3 pc) |
| Absolute magnitude (MV) | −2.24[6] |
| Details | |
| η Lup A | |
| Mass | 7.0±0.2[7] M☉ |
| Radius | 6.7[8] R☉ |
| Luminosity | 1,729[9] L☉ |
| Temperature | 14,668[9] K |
| Rotational velocity (v sin i) | 242[10] km/s |
| Age | 39.8±9.2[7] Myr |
| Other designations | |
| η Lup, CD−38°10797, HD 143118, HIP 78384, HR 5948, SAO 207208[11] | |
| Database references | |
| SIMBAD | data |
The inner pair in this triple system has an estimated orbital period of around 27,000 years.[12] As of 2013, they had an angular separation of 15.0 arc seconds along a position angle of 19°.[3] The primary star, component A, is an evolving A-type subgiant star with a stellar classification of B2 IV.[4] It has used up the supply of hydrogen at its core and has begun to expand off the main-sequence.
The secondary, component B, is a chemically peculiar A-type main sequence star with a class of A5 Vp[4] and an estimated mass 2.10 times that of the Sun.[12] The outer member, component C, has an orbital period of around half a million years.[12] As of 2007, it had an angular separation of 115.8 arc seconds along a position angle of 248° from the primary.[3] It is an F-type main sequence star with a classification of F5 V and an estimated 1.29 times the Sun's mass.[12]