HD 122563

HD 122563
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 02m 31.84551s[1]
Declination +09° 41′ 09.9444″[1]
Apparent magnitude (V) 6.20[2]
Characteristics
Spectral type G8:III: Fe-5[3]
U−B color index +0.38[2]
B−V color index +0.90[2]
V−R color index 0.50
R−I color index 0.58
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)−26.39[5] km/s
Proper motion (μ) RA: −189.539[1] mas/yr
Dec.: −70.415[1] mas/yr
Parallax (π)3.0991 ± 0.0332 mas[1]
Distance1,050 ± 10 ly
(323 ± 3 pc)
Absolute magnitude (MV)−0.69[6]
Details
Mass0.86[6] M☉
Radius23.5[1] R☉
Luminosity787[1] L☉
Surface gravity (log g)1.60[6] cgs
Temperature4,598[6] K
Metallicity [Fe/H]−2.60[7] dex
Rotational velocity (v sin i)5.0[7] km/s
Age12.6[6] Gyr
Other designations
BD+10°2617, HIP 68594, HD 122563, HR 5270, SAO 120251
Database references
SIMBADdata

HD 122563 is an extremely metal-poor red giant star, and the brightest metal-poor star in the sky. Its low heavy element content was first recognized by spectroscopic analysis in 1963.[8] For more than twenty years it was the most metal-poor star known, being more metal-poor than any known globular cluster, and it is the most accessible example of an extreme population II or Halo star.

As the most extreme metal-poor star known, HD 122563's composition was crucial in constraining theories for galactic chemical evolution; in particular, its composition peculiarities provided signposts for understanding the accumulation of heavy elements by stellar nucleosynthesis in the Galaxy. For example, it has an excess of oxygen, [O/Fe] = +0.6,[9] while the proportions of strontium, yttrium, zirconium, barium and the lanthanide elements suggest that the s-process has made no contribution to the material present in the star: in HD 122563, all these elements are products of the r-process instead.[10] The implication is that the star formed at a time and place where there had not been enough time for any previous generation of stars to have produced s-process elements, though there was r-process material present.

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  4. ^ NSV 6526
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  6. ^ a b c d e Cite error: The named reference creevey2012 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference cortes2009 was invoked but never defined (see the help page).
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  10. ^ Cite error: The named reference apj267_757 was invoked but never defined (see the help page).