Astronomers Discover ‘Gold Standard’ Star in Milky Way

There is a relatively bright star in our sun’s neighborhood of the Milky Way Galaxy. Inside of it, astronomers have been able to identify the widest variety of elements in a star more than our solar system yet.

The research, led by University of Michigan astronomer Ian Roederer, has identified 65 elements in the star HD 222925. Forty-two of the elements detected are heavy elements listed along the lowest part of the table of elements.

Distinguishing these elements in one star will help astronomers understand the “rapid neutron capture process,” or one of the main ways that heavy elements in deep space were created. Their results are posted on arXiv and approved for publication in the Astrophysical Journal Supplement Series.

Rapid neuron capture

“To the best of my knowledge, that is a record for any object beyond our solar system, and what makes this star so unique is that it has an extremely high relative percentage of the elements listed along the bottom two-thirds of the periodic table. We also detected gold,” Roederer said. “These elements were made by the fast neutron capture process. That is the thing we are trying to study: the physics in understanding how, where and when those elements were made.”

The process also called the “r-process,” starts with the presence of lighter elements such as iron. After that, rapidly– on the order of a second– neutrons are included in the nuclei of the lighter elements. According to the astronomers, this develops heavier elements such as selenium, silver, tellurium, platinum, gold, and thorium, the kind located in HD 222925, all of which are seldom found in stars.

“You need lots of free neutrons and a very high energy set of conditions to liberate them and include them to the nuclei of atoms,” Roederer said. “There are not many environments that it can take place– two, maybe.”

Among these conditions has been confirmed: the combining of neutron stars. Neutron stars are the collapsed cores of supergiant stars and are the tiniest and densest identified celestial materials. The crash of neutron star pairs causes gravitational waves, and in 2017, astronomers first detected gravitational waves from merging neutron stars. One more manner the r-process might happen desires the explosive death of massive stars.

“That is a crucial progression: identifying where the r-process can happen. It is a much bigger step to say, ‘What did that occurrence do? What was produced there?” Roederer said. “That is where our study is required.”

The elements found in the star

The elements Roederer and his team identified in HD 222925 were produced in massive supernovae or a merger of neutron stars early in deep space. The material was removed and thrown back into space, where after was transformed into the star Roederer is currently studying.

This star can at that point be utilized as a proxy wherefore one of those events would have produced. Any type developed in the future that shows how the r-process or nature generates elements on the bottom two-thirds of the table of elements must definitely have the exact signature as HD 222925, Roederer declares.

Crucially, the astronomers used a device on the Hubble Space Telescope that collects ultraviolet spectra. This device was essential in enabling the astronomers to collect light in the ultraviolet part of the light spectrum– light that is faint, coming from a cool star such as HD 222925.

The astronomers also utilized one of the Magellan telescopes– a consortium of which U-M is a partner– at Las Campanas Observatory in Chile to collect light from HD 222925 in the optical part of the light spectrum.

These spectra inscribe the “chemical fingerprint” of elements within stars. Reading these spectra permits the astronomers to detect the components included in the star and just how much of a component the star has.

Further research

Anna Frebel is a co-author of the research and professor of physics at the Massachusetts Institute of Technology. She assisted with the general interpretation of the HD 222925’s element abundance pattern and how it notifies our understanding of the beginning of the components in the cosmos.

“We now know the detailed element-by-element output of some r-process occurrence that occurred early in the universe,” Frebel said. “Any model that tries to comprehend what is happening with the r-process has to be able to reproduce that.”

Most of the study co-authors belong to a team called the R-Process Alliance, a group of astrophysicists dedicated to addressing the significant concerns of the r-process. This project notes one of the group’s key objectives: discovering which elements and in what quantities were created in the r-process in an unprecedented degree of detail.

Read the original article on Science Daily.

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