HD 222925

HD 222925 is a horizontal branch star about 1,470 light years away in the southern constellation Tucana. It is magnitude 9, far below naked-eye visibility. It is an Ap star, a type of chemically peculiar star with an over-abundance of certain metals in its spectrum.

HD 222925

Elements detected in HD 222925 totalling 65 with 42 coming from the r-process (31 ≤ Z ≤ 92) . Elements with no long-lived isotopes are indicated using the light gray font.[1]
Observation data Epoch J2000.00      Equinox J2000.00
Constellation	Tucana
Right ascension	23h 45m 17.607s[2]
Declination	−61° 54′ 42.84″[2]
Apparent magnitude (V)	9.03[3]
Characteristics
Evolutionary stage	horizontal branch
Spectral type	F8 Sr Eu[4] (ApSrEu)[5]
Astrometry
Radial velocity (Rv)	−38.9±0.6[6] km/s
Proper motion (μ)	RA: 143.803[2] mas/yr Dec.: −99.109[2] mas/yr
Parallax (π)	2.2202±0.0117 mas[2]
Distance	1,469 ± 8 ly (450 ± 2 pc)
Details
Mass	0.75±0.20[6] M☉
Radius	6[7] R☉
Luminosity	43[4] L☉
Surface gravity (log g)	2.54±0.17[1] cgs
Temperature	5,636±103[1] K
Metallicity [Fe/H]	−1.47±0.08[6] dex
Other designations
CD−62°1462, HD 222925, HIP 117168
Database references
SIMBAD	data

HD 222925 has been referred to as the 'gold standard star' by the media.^[8] In 2022, astronomers from the University of Michigan identified 65 elements in the star (including gold), a turning point to help the scientific community understand the rapid neutron capture process.^[9] The elements were produced in a massive supernova or a merger of neutron stars early in the universe, and it was ejected into space where it later reformed into the current star.^[10]

Gallery

• 
  Wavelength for each element detected by atomic number with each spectral line represented as a dot. A gap between ≈3145 Å and ≈3330 Å reflecting an atmospheric cutoff between STIS and MIKE spectra.^[1]
• 
  This mosaic shows two GHOST spectra of HD 222925.^[11]