Astronomers have described a record number of elements in the composition of a distant star

(ORDO NEWS) — A detailed list of elements and their quantities will help to understand the r-process, the most common scenario in the Universe for the formation of elements heavier than iron.

Astronomers have identified 65 elements in the old star HD 222925, located in the halo of the Milky Way. Of these, 42 are heavy elements like silver and gold.

By the time the universe cooled after the Big Bang, only the simplest chemical elements had managed to form in it. Stars have slightly expanded this diversity through fusion in their interiors. And yet, the main part of the periodic table was “born” in supernova explosions and collisions of neutron stars.

The formation of heavy elements in this case most often occurs due to successive capture of neutrons. This requires a large number of these elementary particles and high-energy conditions in which neutrons can separate and attach to the nuclei of atoms.

This so-called r-process always takes place in a fraction of a second – faster than radioactive decay has time to occur. This is how a variety of heavy elements formed in HD 222925 , including tungsten, iridium, platinum and gold.

Such heavy elements are rarely detected even in stars enriched in the r-process. And HD 222925 is one of the brightest such stars known, which is why scientists are so interested.

The team began describing its heavy elements a few years ago using the optical spectrum. It was possible to expand this list due to Hubble observations in the ultraviolet spectrum. A detailed composition will allow you to understand the conditions under which a star was formed.

“As far as I know, this is a record [number of identified elements] for an object outside the solar system. The star is unique in that a significant proportion of its elements are in the bottom two-thirds of the periodic table, explains Ian Roederer , an astronomer at the University of Michigan.

“These elements were formed during a fast neutron capture process. That’s what we’re trying to study: the physics of how, where, and when these elements formed.”

The elements in HD 222925 were formed either in the explosion of a massive supernova or during the merger of neutron stars in the young Universe. The main thing is that such a detailed composition can be used to test hypotheses and models of the r-process.

“Now we know a detailed list of elements that came out of some kind of r-process that happened in the young universe,” says co-author Anna Frebel , professor of physics at the Massachusetts Institute of Technology. “Any model that will describe the r-process will also have to reproduce this result.”

Many of the authors of the new study are members of the so-called R-Process Alliance, a group of astrophysicists that seeks to answer all questions about the formation of heavy elements so rapidly.

Now they have achieved one of their key goals – they have determined in as much detail as possible which elements and in what quantity are formed during the fast process of neutron capture.


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