- Writing
- BBC News World
image source, H.-W. Rix / MPIA
A team of researchers from the Max Planck Institute for Astronomy (MPIA) identified, in the central regions of our galaxy, the “poor old heart of the Milky Way”.
These were the words they used to refer to a star population that formed in the early history of the Milky Way, more than 12.5 billion years.
The astronomers made this discovery by analyzing the latest information released by the European Space Agency’s Gaia mission, using a neural network to extract the metallicity of two million bright giant stars in the inner regions of our galaxy.
Metallicity is the amount of chemical elements heavier than helium that the star’s atmosphere contains (the lower its metallicity, the older the star).
On a map of the sky, these stars appear to be concentrated around the galactic center.
The distances provided by Gaia (via the parallax method) allow a 3D reconstruction showing those stars confined within a comparatively small region around the center, approximately 30,000 light-years across.
The detection of these stars, as well as the properties that were observed, corroborate cosmological simulations of our galaxy’s earliest history.
As the study researchers explain, these simulations predicted where the ancient stars might be found.
machine learning
To perform the analysis, the astronomers turned to machine learning methods.
In this particular case, the neural network was trained using selected Gaia spectra as input: Gaia spectra for which the correct answer, metallicity, was already known from another study.
The neural network was able to derive precise and exact metallicities even from stars it had never encountered before.
image source, Getty Images
While the insights gained from the analysis of the Gaia data are groundbreaking in that they demonstrate the continued existence of the “poor old heart” of our Milky Way, that discovery raises new questions, such as which parent galaxy of the Milky Way each of the stars belongs to this central region.
The researchers are confident that they will be able to answer this and other questions in the future.
