Astronomers discover ‘gold normal’ star in Milky Means

Pasadena, CA— A staff 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 are printed in The Astrophysical Journal Complement Collection.

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 perceive one of many major strategies by which the universe’s heavy components have been created—speedy neutron seize course of.

“To the most effective of my information, that is a report 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 speedy neutron seize course of. That is actually the factor we’re attempting to review: the physics in understanding how, the place and when these components have been made.”

Many components are fashioned by nuclear fusion, wherein two atomic nuclei fuse collectively and launch vitality, creating a distinct, heavier atom. However components heavier than zinc are made by a course of known as neutron seize, throughout which an current ingredient acquires extra neutrons one by one that then “decay” into protons, altering the make-up of the atom into a brand new ingredient.

Neutrons may 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. Various kinds of components are created by every methodology. Nevertheless it’s the second that is 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 an important function,” Holmbeck mentioned. “Sure sorts of supernovae may presumably additionally produce these heavy components, however that is still 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 fashioned by a neutron star merger or a supernova.

“The extra components recognized on this examine present a brand new baseline that may be in contrast

to simulations, which we will use to disclose the origin story of the heavy components seen in HD 222925’s distinctive chemical signature.”

The fabric the staff 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. Because of this 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 gentle within the ultraviolet a part of the sunshine spectrum—gentle that’s faint, coming from a cool star akin to HD 222925. The astronomers additionally used one of many Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile to gather gentle 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 is going on on with the r-process has to have the ability to reproduce that.”

Most of the examine co-authors are a part of a gaggle known as the R-Course of Alliance, a gaggle of astrophysicists devoted to fixing the massive questions of the r-process. This mission marks one of many staff’s key targets: figuring out which components, and in what quantities, have been produced within the r-process in an correct stage of element.


This work was supported by NASA via 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 US Nationwide Science Basis; the NASA Astrophysics Knowledge Evaluation Program; the US Division of Vitality, and NOIRLab, which is managed by AURA below a cooperative settlement with the NSF.