Q Scorpii
High proper motion binary star system in the constellation of Scorpius
From Wikipedia, the free encyclopedia
Q Scorpii, also designated as HD 159433, is an astrometric binary[12] (100% chance)[13] located in the southern zodiac constellation Scorpius. It has an apparent magnitude of 4.27,[2] making it readily visible to the naked eye under ideal conditions. It lies in the tail of Scorpius, between the stars λ Scorpii and μ Scorpii and is located 7′ away from the faint globular cluster Tonantzintla 2. Based on parallax measurements from Gaia DR3, the system is estimated to be 158 light years distant,[1] but is approaching the Solar System with a heliocentric radial velocity of −49 km/s.[6]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 17h 36m 32.85514s[1] |
| Declination | −38° 38′ 06.8918″[1] |
| Apparent magnitude (V) | 4.27±0.01[2] |
| Characteristics | |
| Evolutionary stage | horizontal branch[3] |
| Spectral type | K0 IIIb[4] |
| U−B color index | +0.90[5] |
| B−V color index | +1.08[5] |
| Astrometry | |
| Radial velocity (Rv) | −49±3[6] km/s |
| Proper motion (μ) | RA: −16.762 mas/yr[1] Dec.: −218.275 mas/yr[1] |
| Parallax (π) | 20.6922±0.2161 mas[1] |
| Distance | 158 ± 2 ly (48.3 ± 0.5 pc) |
| Absolute magnitude (MV) | +0.67[7] |
| Details[8] | |
| Mass | 1.10±0.07 M☉ |
| Radius | 12.39±0.47 R☉ |
| Luminosity | 62.2±4.2 L☉ |
| Surface gravity (log g) | 2.41±0.11 cgs |
| Temperature | 4,605±40 K |
| Metallicity [Fe/H] | −0.28±0.02 dex |
| Rotational velocity (v sin i) | <1[9] km/s |
| Other designations | |
| Q Scorpii, 159 G. Scorpii[10], CD−38°12044, CPD−38°6933, GC 23846, HD 159433, HIP 86170, HR 6546, SAO 209019[11] | |
| Database references | |
| SIMBAD | data |
The visible component is a red giant with a stellar classification of K0 IIIb.[4] The IIIb luminosity class indicates that it is a lower luminosity giant star. Q Scorpii is a red clump star located on the cool end of the horizontal branch,[3] fusing helium at its core. It has 110% the mass of the Sun but has expanded to 12.4 times its girth.[8] It radiates 62 times the luminosity of the Sun from its photosphere at an effective temperature of 4,605 K,[8] giving it an orange hue. Q Scorpii has an iron abundance half of the Sun's, making it metal deficient.[8] Like most giant stars, it spins slowly, having a projected rotational velocity lower than 1 km/s.[9]