A new star rich in precious metals

Astronomers used an instrument on the Hubble Space Telescope that can collect ultraviolet spectra. They were instrumental in allowing astronomers to collect light in the ultraviolet part of the light spectrum.

  • An astronomer has identified 65 elements in the star HD 222925

Astronomers have identified a relatively bright star in the vicinity of the Sun in the Milky Way, in the southern constellation of the Toucan, named HD 222925.

In the context, University of Michigan astronomer Ian Roderer was able to identify 65 elements in the star HD 222925, of which 42 are the heaviest elements listed along the bottom of the periodic table (a tabular arrangement of chemical elements, ordered by their atomic number, electronic distribution, and chemical properties). recurring, whose structure shows periodic trends). This makes HD 222925 a star with the widest known range of specific elements, outside our solar system.

Perhaps identifying these elements in a single star will help astronomers understand the so-called “rapid neutron capture process”, or one of the main ways in which the heavy elements in the universe are formed.

“As far as I know, this is a record for any object outside our solar system,” Roderer said in the study, the results of which are detailed on arXiv. “What makes this star so unique is that it has a very high percentage of the elements listed along the bottom two-thirds of the periodic table.” We discovered gold so that these elements were made through a process of rapid neutron capture. And that’s what we’re really trying to study: the physics of understanding how, where and when these elements were made.”

The process, also called the “R” process (fast neutron capture process), begins with the presence of lighter elements such as iron. Then, neutrons are rapidly added to the nuclei of the lighter elements. This results in heavier elements such as selenium, silver, tellurium, platinum, gold and thorium, the kind found in HD 222925, all of which are rarely detected in stars, according to astronomers.

“We need a lot of free neutrons and a very high set of energy conditions to liberate them and add them to the nuclei of atoms. There are not many environments in which that can happen,” Roderer added.

One such environment, a neutron star merger, was confirmed. Neutron stars are the collapsed cores of giant stars, the smallest and densest known celestial bodies. Colliding pairs of neutron stars cause gravitational waves, and in 2017, astronomers first detected gravitational waves from merging neutron stars. Another way “Operation R” could occur is the explosive death of massive stars.

The elements that Roderer and his team identified in HD 222925 were produced either in a massive supernova or merging neutron stars very early in the universe. The matter was ejected and returned to space, where it was later modified to become the star that Roderer is studying today.

Roderer says that any model developed in the future showing how the “R process” or nature produces elements in the lower two-thirds of the periodic table should have the same signature as HD 222925.

The astronomers used an instrument on the Hubble Space Telescope that can collect ultraviolet spectra. This tool was instrumental in allowing astronomers to collect light in the ultraviolet part of the light spectrum, faint light from a cold star like HD 222925.

The astronomers also used one of the Magellan Telescopes at the Las Campanas Observatory in Chile, a consortium in which the University of Michigan is involved, to collect light from HD 222925 in the optical part of the light spectrum.

These spectra encode the “chemical fingerprint” of the elements within the stars, and reading these spectra allows astronomers not only to determine what elements are in the star, but also how much of the element the star contains.