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.
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] (He was previously detected in NIR spectra by Navarrete et al. (2015).[2])
HD 222925
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]
HD 222925 has been referred to as the 'gold standard star' by the media.[9] 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.[10] 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.[11]
References
Roederer, Ian U.; Lawler, James E.; Den Hartog, Elizabeth A.; Placco, Vinicius M.; Surman, Rebecca; Beers, Timothy C.; Ezzeddine, Rana; Frebel, Anna; Hansen, Terese T.; Hattori, Kohei; Holmbeck, Erika M.; Sakari, Charli M. (2022). "The R-process Alliance: A Nearly Complete R-process Abundance Template Derived from Ultraviolet Spectroscopy of the R-process-enhanced Metal-poor Star HD 222925". The Astrophysical Journal Supplement Series. 260 (2): 27. arXiv:2205.03426. Bibcode:2022ApJS..260...27R. doi:10.3847/1538-4365/ac5cbc. S2CID248571656.
Bailer-Jones, C. A. L.; etal. (2011). "Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry". Monthly Notices of the Royal Astronomical Society. 411 (1): 435–452. arXiv:1009.2766. Bibcode:2011MNRAS.411..435B. doi:10.1111/j.1365-2966.2010.17699.x. S2CID30425562.
Cunha, M. S.; etal. (2019). "Rotation and pulsation in Ap stars: First light results from TESS sectors 1 and 2". Monthly Notices of the Royal Astronomical Society. 487 (3): 3523. arXiv:1906.01111. Bibcode:2019MNRAS.487.3523C. doi:10.1093/mnras/stz1332.
Houk, Nancy (1975). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol.1. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1975mcts.book.....H.
Roederer, Ian U.; Sakari, Charli M.; Placco, Vinicius M.; Beers, Timothy C.; Ezzeddine, Rana; Frebel, Anna; Hansen, Terese T. (2018). "The R-Process Alliance: A Comprehensive Abundance Analysis of HD 222925, a Metal-poor Star with an Extreme R-process Enhancement of [Eu/H] = -0.14". The Astrophysical Journal. 865 (2): 129. arXiv:1808.09469. Bibcode:2018ApJ...865..129R. doi:10.3847/1538-4357/aadd92. S2CID119046070.
Cruzalèbes, P.; Petrov, R. G.; Robbe-Dubois, S.; Varga, J.; Burtscher, L.; Allouche, F.; Berio, P.; Hofmann, K. H.; Hron, J.; Jaffe, W.; Lagarde, S.; Lopez, B.; Matter, A.; Meilland, A.; Meisenheimer, K.; Millour, F.; Schertl, D. (2019). "A catalogue of stellar diameters and fluxes for mid-infrared interferometry". Monthly Notices of the Royal Astronomical Society. 490 (3): 3158–3176. arXiv:1910.00542. Bibcode:2019MNRAS.490.3158C. doi:10.1093/mnras/stz2803. S2CID203610229.
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