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How do stars destroy lithium? Was a drastic change in the shape of the Milky Way caused by the sudden arrival of millions of stellar illegal immigrants?
These are just some of the astronomical questions that will likely be answered after today’s release of “GALAH DR3”, the largest stellar chemical data set ever compiled.
The data, which includes over 500GB of information gathered from more than 30 million individual measurements, was collected by astronomers including Sarah Martell from UNSW and colleagues from the ARC Center of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D) . They used the Anglo Australian Telescope (AAT) at the Australian Astronomical Observatory in Siding Spring in rural New South Wales.
The release is the third of the Galactic Archeology with HERMES (GALAH) project, which aims to study star formation, chemical enrichment, migration and mergers in the Milky Way. It does this using an instrument called a high-efficiency, high-resolution multi-element spectrograph, or HERMES, which is connected to the AAT.
The new data covers 600,000 stars and brings the project very close to achieving its goal of detecting one million.
“It’s kind of like a galactic version of the Cluedo game,” said Sven Buder of ASTRO 3D, a researcher at Australian National University.
“The chemical information we’ve gathered is quite similar to stellar DNA – we can use it to figure out where each star is coming from. We can also determine their age and movements and provide a deeper understanding of how the Milky Way has evolved. “
And, just like in Cluedo, information can be used to get to the bottom of mysterious events.
“For example, while we’re mainly surveying our solar neighborhood, we’ve found more than 20,000 stars that don’t have the same chemical composition or age our Sun and its neighbors,” said Dr. Buder.
“We know that about eight billion years ago the shape of the Milky Way changed dramatically when it collided with another smaller galaxy, which contained millions of stars. We’ve now used stellar DNA to identify some of the prime suspects in the assault. These illegal immigrants are so different that they can only come from somewhere else. “
Solve cosmological puzzles
As with the two previous data released by the GALAH survey, the information is freely available to astronomers around the world.
“Making large datasets like GALAH DR3 widely available is really important for astronomical research,” explains associate professor Sarah Martell of UNSW and ASTRO 3D.
“Since the start of the GALAH project we have focused on creating a dataset that can answer our questions about the history of the Milky Way, and many more as well. I am excited to see what our international colleagues will do with GALAH DR3.” .
The previous release of data from the GALAH project, known of course as DR2, took place in 2018. It has fueled a number of significant discoveries regarding the evolution of the Milky Way, the existence of exoplanets, hidden star clusters and many more.
Another mystery that will probably be solved soon thanks to the new evidence uncovered is called “Cosmological Lithium Puzzle”.
Lithium was one of the elements created during the Big Bang. It is also destroyed by some types of stars. However, modeling aimed at estimating their abundance has so far always proved insufficient, with the calculated total not matching the empirical evidence.
GALAH DR3 appears to offer a solution.
“Basically, many of the older stars burned much of the Big Bang’s lithium, so our measurements for this element are less than the amount initially synthesized in the early Universe,” said Dr. Sanjib Sharma, researcher at ASTRO 3D at the University. of Sydney.
“At the same time, we found that a type of star, known as evolved giants, should have burned virtually all of its lithium by now, but many of them have a lot more of it than we expected. The GALAH data will help us find out why. “
More than 100 scientists are collaborating on the GALAH project. They are based in several universities in Australia, Italy, the United Kingdom, Slovenia, the United States, Hungary, Sweden, the Netherlands and Germany.
The GALAH DR3 data set can be found online.
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