Xi Herculis
Star in the constellation Hercules
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Xi Herculis is a solitary[11] star located within the northern constellation of Hercules. The star is visible to the naked eye with an apparent visual magnitude of 3.70.[2] Based upon an annual parallax shift of 23.85 mas as seen from Earth, it is located 137 light years from the Sun.[1] At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.05 due to interstellar dust. It is a suspected member of the Sirius stream of co-moving stars.[12]
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hercules |
| Right ascension | 17h 57m 45.88567s[1] |
| Declination | +29° 14′ 52.3660″[1] |
| Apparent magnitude (V) | 3.70[2] |
| Characteristics | |
| Evolutionary stage | red clump[3] |
| Spectral type | G8 III[4] |
| U−B color index | +0.66[2] |
| B−V color index | +0.93[2] |
| Astrometry | |
| Radial velocity (Rv) | −1.65±0.17[5] km/s |
| Proper motion (μ) | RA: 81.919 mas/yr[1] Dec.: −18.962 mas/yr[1] |
| Parallax (π) | 23.8544±0.1068 mas[1] |
| Distance | 136.7 ± 0.6 ly (41.9 ± 0.2 pc) |
| Absolute magnitude (MV) | +0.62[6] |
| Details | |
| Mass | 2.01[7] M☉ |
| Radius | 9.94±0.09[8] R☉ |
| Luminosity | 57.2±2.1[8] L☉ |
| Surface gravity (log g) | 2.87±0.09[9] cgs |
| Temperature | 5,032±48[8] K |
| Metallicity [Fe/H] | +0.09±0.04[9] dex |
| Rotation | 67[3] d |
| Rotational velocity (v sin i) | 2.8[5] km/s |
| Age | 2.48[7] Gyr |
| Other designations | |
| ξ Her, 92 Her, BD+29°3156, HD 163993, HIP 87933, HR 6703, SAO 85590[10] | |
| Database references | |
| SIMBAD | data |
This is an evolved G-type giant star with a stellar classification of G8 III.[4] It is a red clump star, which means it is on the horizontal branch and generating energy through the thermonuclear fusion of hydrogen at its core. The star is emitting X-rays with a luminosity of 3.03×1030 erg s−1 in the 0.3–10 keV band.[3] It has twice[7] the mass of the Sun but, at the age of two and a half billion years,[7] it has expanded to 10 times the Sun's radius. The star is radiating 57 times the solar luminosity from its photosphere at an effective temperature of 5,032 K.[8]
Xi Herculis was discovered to be a variable star when the Hipparcos data was analyzed.[14] It is a semiregular variable star, oscillating in brightness by 3 hundredths of a magnitude, over a period of 120.8 days.[15]
Chinese name
Markov 1, the mini teapot
One third of a degree to the north-northwest of Xi Herculis is the location of a telescopic asterism in the shape of a teapot. This teapot (Markov 1) could be seen as a somewhat twisted small equivalent of the large and easy to recognize teapot asterism in the constellation Sagittarius.[citation needed]