Astronomers have uncovered a star, referred to as HD 222925, that has the widest vary of components but noticed in a star past our personal Solar. They've recognized 65 components within the star, together with 42 from the underside of the periodic desk.
A workforce of astronomers led by College of Michigan’s Ian Roederer and together with Carnegie’s Erika Holmbeck have recognized the widest vary of components but noticed in a star past our personal Solar. Their findings might be printed in The Astrophysical Journal Complement Sequence.
The researchers recognized 65 components within the star, which is named HD 222925. Of those, 42 are from the underside of the periodic desk. Their identification will assist astronomers higher perceive fast neutron seize course of — one of many primary strategies by which the universe’s heavy components have been created.
“To the most effective of my data, that’s a file for any object past our Photo voltaic System. And what makes this star so distinctive is that it has a really excessive relative proportion of the weather listed alongside the underside two-thirds of the periodic desk. We even detected gold,” defined Roederer, a former Carnegie postdoc. “These components have been made by the fast neutron seize course of. That’s actually the factor we’re attempting to review: the physics in understanding how, the place and when these components have been made.”
The star HD 222925 is a ninth-magnitude star situated towards the southern constellation Tucana. Credit score: The STScI Digitized Sky Survey
Many components are shaped by nuclear fusion, wherein two atomic nuclei fuse collectively and launch power, creating a unique, heavier atom. However components heavier than zinc are made by a course of referred to as neutron seize, throughout which an current ingredient acquires further neutrons one after the other that then “decay” into protons, altering the make-up of the atom into a brand new ingredient.
Neutrons might be captured slowly, over lengthy intervals of time contained in the star, or in a matter of seconds, when a catastrophic occasion causes a burst of neutrons to bombard an space. Several types of components are created by every technique. But it surely’s the second that’s of curiosity to this analysis.
“Astronomers debated for a few years about what phenomena may set off such a bombardment and in 2017 it was confirmed that heavy components could possibly be created by the collision of two neutron stars—a discovery wherein Carnegie astronomers performed a vital position,” Holmbeck mentioned. “Sure varieties of supernovae may presumably additionally produce these heavy components, however that continues to be to be observationally confirmed.”
Holmbeck is engaged on a follow-up paper to find out whether or not the chemical abundances noticed in HD 222925 have been shaped by a neutron star merger or a supernova.
“The extra components recognized on this examine present a brand new baseline that may be in comparison with simulations, which we are able to use to disclose the origin story of the heavy components seen in HD 222925’s distinctive chemical signature.”
The fabric the workforce recognized in HD 222925 was synthesized very early within the universe’s youth. It was ejected and thrown again into area, the place it later reformed into the star they have been finding out. Which means HD 222925 can be utilized as a proxy for what a neutron star merger or supernova would have produced.
Crucially, the astronomers used an instrument on the Hubble Area Telescope that may accumulate ultraviolet spectra. This was key in permitting the astronomers to gather mild within the ultraviolet a part of the sunshine spectrum—mild that's faint, coming from a cool star corresponding to HD 222925. The astronomers additionally used one of many Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile to gather mild from HD 222925 within the optical a part of the sunshine spectrum.
These spectra encode the “chemical fingerprint” of components inside stars, and studying these spectra permits the astronomers not solely to establish the weather contained within the star, but additionally how a lot of a component the star comprises.
“We now know the detailed element-by-element output of some r-process occasion that occurred early within the universe,” mentioned co-author Anna Frebel of MIT. “Any mannequin that tries to grasp what’s happening with the r-process has to have the ability to reproduce that.”
Most of the examine co-authors are a part of a gaggle referred to as the R-Course of Alliance, a gaggle of astrophysicists devoted to fixing the large questions of the r-process. This undertaking marks one of many workforce’s key targets: figuring out which components, and in what quantities, have been produced within the r-process in an unprecedented degree of element.
Reference: “The R-Course of Alliance: A Almost Full R-Course of Abundance Template Derived from Ultraviolet Spectroscopy of the R-Course of-Enhanced Steel-Poor Star HD 222925” by Ian U. Roederer, James E. Lawler, Elizabeth A. Den Hartog, Vinicius M. Placco, Rebecca Surman, Timothy C. Beers, Rana Ezzeddine, Anna Frebel, Terese T. Hansen, Kohei Hattori, Erika M. Holmbeck and Charli M. Sakari, Accepted, The Astrophysical Journal Complement Sequence.
arXiv:2205.03426
This work was supported by NASA by means of grants from the Area Telescope Science Institute, which is operated by the Affiliation of Universities for Analysis in Astronomy, Integrated, below a NASA contract; the U.S. Nationwide Science Basis; the NASA Astrophysics Knowledge Evaluation Program; the U.S. Division of Vitality, and NOIRLab, which is managed by AURA below a cooperative settlement with the NSF.
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