“Jewel of Star Archaeology”: They discover that one of the oldest stars is binary

An international team of researchers has confirmed that an ancient star in the Milky Way is, to their surprise, a double or binary starwhich was discarded in this type of primitive objects.

Stars with a lower metal content They are considered the oldest in the Milky Way, having formed just a few hundred million years after the Big Bang, once considered fleeting compared to the age of the Universe, the Instituto de Astrofísica de Canarias (IAC) specified on Tuesday. it’s a statement.

These stars are real living fossils which have encoded in their chemical composition the first stages of the evolution of the Universe and specifically the one that has been studied, the star SMSS1605-1443, was discovered in 2018 and identified as one of the oldest in the galaxy due to its chemical composition , but its true nature was unknown.

Now, thanks to the joint effort of several European research groups and the use of the ESPRESSO spectrograph, the origin of “this jewel of stellar archeology”.

The results of this research were published today in the journal Astronomy & Astrophysics (A&A).

“It was a surprise to discover, thanks to ESPRESSO and the VLT, what this object really was a double (or binary) star, something not until recently believed to occur in most of these very old stars”, says David Aguado, lead author of this work and researcher at the University of Florence.

The research team used the ESPRESSO tool which, given its high precision, made it possible to follow the small variations in the speed of this star, which confirm its binary nature but leave that of its companion open.

These types of stars are believed to have formed from material processed inside the first massive stars, ejected in supernova explosions early in the formation of the Milky Way.

Consequently, these stars are low in iron but a high carbon contentgenerated within the first massive stars.

The high resolution of the ESPRESSO instrument made it possible to analyze in detail the relative composition of carbon isotopes, which provides new information on the origin of this object.

IAC researcher Jonay González, co-author of this work, clarifies that the key was given by the ratio of carbon-12 to carbon-13 found in the atmosphere of this star, since the relative amount of these two isotopes demonstrates that the internal processes of the stella have not altered its original composition.

“It’s like having an intact sample of what the environment was like in which this star formed more than 10,000 million years ago,” says the astrophysicist.

This discovery should be understood in the context of a project that began a decade ago in which we studied in detail all known stars of this rare class until we found this wonderful discovery, which helps us better understand evolution. Universe, reports Carlos Allende, IAC researcher and co-author of this work.

Rafael Rebolo, director of the IAC and another of the authors of this work, points out that the multidisciplinary team that was formed with researchers from Spain, Italy, France, Portugal and Switzerland has highlighted that the ESPRESSO spectrograph “is one of the best and more modern tools to study the formation of the first stars”.

EFE extension