Understanding our universe requires the one-two punch of combining observations and models and refining our understanding until those theory-driven models resemble the observations. And when the models reveal things beyond our observations’ abilities, sometimes we have to do more observing.

And for one team of researchers, “more observing” has led to the publication of a 25-million-star catalog that documents the chemical evolution of our galaxy.

As the story goes, our universe formed with a mixture of hydrogen, helium, and trace amounts of lithium and beryllium. Larger atoms have been created inside subsequent generations of stars and in bursts of fusion at the moments of their death by supernova or merger with another star. Since different kinds of stars create different kinds and proportions of atoms, we should be able to trace the history of our galaxy by looking at the distribution of different atoms in stars that formed at different times.

And now, 25 million stellar spectra later, researchers can begin to key in on details. According to lead researcher Tim Beers: The elemental abundances of individual stars trace the chemical enrichment of the Milky Way galaxy, from when it first began to form stars shortly after the Big Bang to the present. Combining this information with the stellar distances and motions allows us to constrain the origin of different components in the galaxy, such as the halo and disk populations. Adding age estimates puts a `clock’ on the process so that a much more complete picture of the entire process can be drawn.

Analysis of this catalog will lead to a richer understanding of the origins of different parts of our galaxy, and when those results are published, we’ll bring them to you here on the Daily Space.

With 25 million stars to study, we know there will be weird things to learn. Sometimes, just looking at one kind of object can create a massive mystery!

More Information

University of Notre Dame press release

“Beyond Spectroscopy. I. Metallicities, Distances, and Age Estimates for Over 20 Million Stars from SMSS DR2 and Gaia EDR3,” Yang Huang et al., 2022 February 3, The Astrophysical Journal