March 28, 2023

Rapid Neutron Capture: Astronomers Discover “Gold Standard” Star in Milky Way

The star HD 222925 is a ninth-magnitude star located towards the southern constellation Tucana. Credit: The STScI Digitized Sky Survey
Numerous elements are formed by nuclear blend, in which two atomic nuclei fuse together and release energy, producing a various, heavier atom. Elements heavier than zinc are made by a procedure called neutron capture, throughout which an existing element obtains additional neutrons one at a time that then “decay” into protons, altering the makeup of the atom into a new component.
Neutrons can be captured gradually, over extended periods of time inside the star, or in a matter of seconds, when a devastating event causes a burst of neutrons to bombard a location. Different types of aspects are developed by each technique. But its the second one thats of interest to this research study.
” Astronomers disputed for several years about what phenomena might trigger such a barrage and in 2017 it was validated that heavy elements might be produced by the collision of 2 neutron stars– a discovery in which Carnegie astronomers played an essential role,” Holmbeck said. “Certain kinds of supernovae could potentially also produce these heavy components, but that stays to be observationally confirmed.”
Holmbeck is working on a follow-up paper to identify whether the chemical abundances observed in HD 222925 were formed by a neutron star merger or a supernova.
” The extra components identified in this study offer a new standard that can be compared to simulations, which we can use to reveal the origin story of the heavy elements seen in HD 222925s special chemical signature.”
The product the group determined in HD 222925 was manufactured really early in deep spaces youth. It was ejected and tossed back into area, where it later on reformed into the star they were studying. This indicates that HD 222925 can be used as a proxy for what a neutron star merger or supernova would have produced.
Crucially, the astronomers utilized an instrument on the Hubble Space Telescope that can gather ultraviolet spectra. This was type in allowing the astronomers to collect light in the ultraviolet part of the light spectrum– light that is faint, originating from a cool star such as HD 222925. The astronomers likewise utilized among the Magellan telescopes at Carnegies Las Campanas Observatory in Chile to collect light from HD 222925 in the optical part of the light spectrum.
These spectra encode the “chemical finger print” of components within stars, and checking out these spectra enables the astronomers not just to identify the elements included in the star, however also just how much of an element the star contains.
” We now know the detailed element-by-element output of some r-process event that occurred early in the universe,” said co-author Anna Frebel of MIT. “Any model that tries to comprehend whats happening with the r-process needs to have the ability to replicate that.”
Much of the research study co-authors belong to a group called the R-Process Alliance, a group of astrophysicists dedicated to fixing the huge questions of the r-process. This job marks one of the groups key goals: determining which aspects, and in what amounts, were produced in the r-process in an unmatched level of detail..
Referral: “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” 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 Supplement Series.arXiv:2205.03426.
This work was supported by NASA through grants from the Space Telescope Science Institute, which is run by the Association of Universities for Research in Astronomy, Incorporated, under a NASA contract; the U.S. National Science Foundation; the NASA Astrophysics Data Analysis Program; the U.S. Department of Energy, and NOIRLab, which is managed by AURA under a cooperative arrangement with the NSF.

Astronomers have actually discovered a star, called HD 222925, that has the best series of components yet observed in a star beyond our own Sun. They have actually identified 65 elements in the star, consisting of 42 from the bottom of the routine table.
A group of astronomers led by University of Michigans Ian Roederer and including Carnegies Erika Holmbeck have determined the best variety of elements yet observed in a star beyond our own Sun. Their findings will be published in The Astrophysical Journal Supplement Series.
The scientists identified 65 aspects in the star, which is called HD 222925. Of these, 42 are from the bottom of the table of elements. Their recognition will assist astronomers better understand fast neutron capture process– one of the primary techniques by which deep spaces heavy elements were created.
And what makes this star so special is that it has an extremely high relative proportion of the aspects listed along the bottom two-thirds of the regular table. “These aspects were made by the fast neutron capture procedure.

The scientists determined 65 elements in the star, which is called HD 222925. Their identification will help astronomers much better understand quick neutron capture process– one of the main methods by which the universes heavy aspects were developed.
And what makes this star so unique is that it has a very high relative proportion of the elements noted along the bottom two-thirds of the routine table. “These components were made by the fast neutron capture procedure. Thats actually the thing were trying to study: the physics in comprehending how, where and when those components were made.”