Xi Hydrae, Latinised from ξ Hydrae, is a solitary star in the

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator ** equatorial orbit **equatorial coordinate system ** equatorial mount, of telescopes * equatorial ...

constellation of Hydra. It was also given the

Flamsteed designation A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England. They are named for John Flamsteed who first used them while co ...

19 Crateris. This magnitude 3.54 star is situated 130 light-years from Earth and has a radius about 10 times that of the Sun. It is radiating 58 times as much luminosity as the Sun. Flamsteed gave Xi Hydrae the designation 19 Crateris. He included a number of stars now within the

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

boundaries of Hydra as part of a ''Hydra & Crater'' constellation overlapping parts of both

modern constellations In contemporary astronomy, 88 constellations are recognized by the International Astronomical Union (IAU). Each constellation is a region of the sky, bordered by arcs of right ascension and declination. Together they cover the celestial sph ...

. The star Xi Hydrae is particularly interesting in the field of asteroseismology since it shows

solar-like oscillations Solar-like oscillations are oscillations in stars that are excited in the same way as those in the Sun, namely by turbulent convection in its outer layers. Stars that show solar-like oscillations are called solar-like oscillators. The oscillations a ...

. Multiple frequency oscillations are found with periods between 2.0 and 5.5 hours. 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 The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass sta ...

for a star with an initial mass around . This puts its age at about .

References

External links

Wisky.org Star Catalogue

The Ultrabass Sounds of the Giant Star Xi Hya.
Listen to Xi Hya (wav).
{{DEFAULTSORT:Xi Hydrae Hydrae, Xi Hydra (constellation) Hydrae, 288 100407 056343 4450 Crateris, 19 Durchmusterung objects G-type giants