Astronomers map 12 billion years of a spiral galaxy’s evolution

Monday 23 March 2026 - 14:50

By: Dakir Madiha

Astronomers map 12 billion years of a spiral galaxy’s evolution

Astronomers have reconstructed the full 12 billion year history of a spiral galaxy for the first time, offering new insight into how galaxies form and evolve over cosmic time.

The study, led by the Center for Astrophysics Harvard and Smithsonian and published in Nature Astronomy, focuses on the massive barred spiral galaxy NGC 1365. Researchers used a technique known as extragalactic archaeology, analyzing chemical signatures in the galaxy’s gas to trace its formation and development.

Using high resolution data from the TYPHOON survey and observations from the Irénée du Pont telescope at Las Campanas Observatory in Chile, the team was able to study individual star forming regions across the galaxy. This level of detail allowed scientists to map variations in oxygen abundance, a key indicator of stellar evolution and galactic history.

By comparing these observations with simulations from the Illustris project, which includes tens of thousands of modeled galaxies, researchers identified a close match. This enabled them to reconstruct NGC 1365’s likely evolutionary path, including its growth through mergers and accumulation of gas over billions of years.

The findings show that the galaxy began as a smaller system and expanded through repeated collisions with dwarf galaxies. Its central region formed early and became enriched with heavier elements, while its outer disk developed gradually as gas and stars were accreted over time. The outer spiral arms appear to have formed more recently, shaped by material drawn from absorbed galaxies.

Scientists say the results confirm that galaxy formation is strongly influenced by mergers and long-term chemical evolution. The close alignment between simulations and observed data also strengthens confidence in current models of cosmic structure formation.

Because NGC 1365 shares similarities with the Milky Way, the method could help researchers determine whether our own galaxy followed a typical evolutionary path or developed under unique conditions. The team plans to apply the technique to other galaxies to test how common these formation patterns are.

The study highlights the growing ability of astronomers to combine observational data and computational models to reconstruct the history of the universe with increasing precision.