Xi Hydrae
Star in the constellation Hydra
From Wikipedia, the free encyclopedia
Xi Hydrae, Latinised from ξ Hydrae, is a solitary[11] star in the equatorial constellation of Hydra. With an apparent magnitude of 3.54[3] it is visible to the naked eye. Based on parallax measurements, the star is situated 130 light-years from Earth.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra[1] |
| Right ascension | 11h 33m 00.11505s[2] |
| Declination | −31° 51′ 27.4435″[2] |
| Apparent magnitude (V) | 3.54[3] |
| Characteristics | |
| Spectral type | G7 III[3] |
| Astrometry | |
| Radial velocity (Rv) | −4.90±0.30[4] km/s |
| Proper motion (μ) | RA: −209.62[2] mas/yr Dec.: −40.84[2] mas/yr |
| Parallax (π) | 25.16±0.16 mas[2] |
| Distance | 129.6 ± 0.8 ly (39.7 ± 0.3 pc) |
| Absolute magnitude (MV) | +0.54[1] |
| Details | |
| Mass | 2.94±0.15[5] M☉ |
| Radius | 10.28±0.11[6] R☉ |
| Luminosity | 61.0±1.5[6] L☉ |
| Surface gravity (log g) | 2.78±0.07[6] cgs |
| Temperature | 5,034±34[6] K |
| Metallicity [Fe/H] | +0.16±0.20[5] dex |
| Rotational velocity (v sin i) | 2.7[7] km/s |
| Age | 510[8] Myr |
| Other designations | |
| ξ Hya, 288 G. Hydrae,[9] CD−31°9083, HD 100407, HIP 56343, HR 4450, SAO 202558[10] | |
| Database references | |
| SIMBAD | data |
Flamsteed gave Xi Hydrae the designation 19 Crateris. He included a number of stars now within the IAU boundaries of Hydra as part of a Hydra & Crater constellation overlapping parts of both modern constellations.[12]
Charactertistics
Xi Hydrae has left the main sequence, having exhausted the supply of hydrogen in its core. Its spectrum is that of a red giant. Modelling its physical properties against theoretical evolutionary tracks shows that it has just reached the foot of the red giant branch for a star with an initial mass around 3 M☉. This puts its age at about 510 Myr.[8] The star has 10.28 times the Sun's radius, 61 times the Sun's luminosity and an effective temperature of 5,034 K.[6]
The star Xi Hydrae is particularly interesting in the field of asteroseismology since it shows solar-like oscillations. Multiple frequency oscillations are found with periods between 2.0 and 5.5 hours.[13]