A huge new dataset will solve several mysteries of the Milky Way

How do the 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, comprising over 500GB of information gathered from over 30 million individual measurements, was collected by astronomers including Sven Buder, Sarah Martell, and Sanjib Sharma of the ARC Center of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3- D) using 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 game Cluedo“said Sven Buder, a researcher at the Australian National University of ASTRO 3-D.

“The chemical information we’ve gathered is pretty similar to stellar DNA – we can use it to tell where each star comes from. We can also determine their age and movements and provide a deeper understanding of how the Milky Way evolved.”

And, just like in Cluedo, the information can be used to get to the bottom of mysterious events.

“For example, while we are mainly surveying our solar neighborhood, we have found more than 20,000 stars that do not have the same chemical composition or age our Sun and its neighbors,” explained 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 have now used stellar DNA to identify some of the prime suspects in the assault. . These illegal immigrants are so different they can only come from somewhere else. “

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, the 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 lithium, so our measurements for this element turn out to be less than the amount initially synthesized in the early Universe,” said ASTRO 3-D researcher Dr. Sanjib Sharma from 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. “.

As with the two previous data released by the GALAH survey, the information is freely available to astronomers around the world.

“Making large datasets such as GALAH DR3 widely available is very important for astronomical research,” explains Associate Professor Sarah Martell of ASTRO 3-D and UNSW Sydney.

“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.” .

Provided by ASTRO 3D