Galactic archaeology uncovers the dramatic history of our next-door neighbor, the Andromeda galaxy

Analysis led by the College of Hertfordshire has revealed the dramatic historical past of Andromeda, our nearest neighboring galaxy. Utilizing state-of-the-art modeling, Professor Chiaki Kobayashi and a staff of worldwide astrophysicists have decided particulars concerning the galaxy’s historical past via galactic archaeology—an method that examines the chemical composition of stars and the event of their host galaxy, to reconstruct its previous.

The research, accepted for publication in The Astrophysical Journal Letters and available on the arXiv preprint server, examines the basic abundances in Andromeda, specifically the presence of each planetary nebulae—fuel and dust which can be shaped from the cast-off outer layers of dying low-mass stars—and red-giant department stars.

The evaluation reveals that Andromeda’s formation was extra dramatic and forceful than that of our personal Milky Way. After an preliminary intense burst of star formation that created the galaxy, a secondary layer of stars was produced between 2 billion and 4.5 billion years in the past, most probably triggered by what scientists name a “moist merger”—a merging of two, gas-rich galaxies that instigates a considerable amount of star formation.

Scientists have lengthy thought it probably that Andromeda skilled a merger of two galaxies, primarily based on the place and movement of particular person stars within the galaxy. Professor Kobayashi’s analysis shines new gentle on the character and influence of such a merger utilizing the chemical composition of stars—and explains how stars and components have been shaped all through the historical past of Andromeda.

Professor Kobayashi, Professor of Astrophysics on the College of Hertfordshire’s Heart for Astrophysics Analysis, stated, “It is a incredible instance of how galactic archaeology can present recent new insights into the historical past of our universe. By analyzing the chemical abundance in numerous ages of stars in Andromeda, we will carry to life its historical past and higher perceive its origins.

“Though in some ways Andromeda is just like our personal Milky Way—it is a similarly-sized, spiral disk galaxy—our new analysis confirms that its history is way extra intense and dramatic, with bursts of exercise forming stars in abundance, and two distinct eras of star formation.”

Professor Kobayashi’s theoretical mannequin predicts two distinct chemical compositions of stars within the two disk parts of Andromeda—one has ten instances extra oxygen than iron, whereas one other has an analogous quantity of oxygen and iron. This modeling has been confirmed by the spectroscopic observations of planetary nebulae, and in addition by these of red-giant stars with the James Webb Area Telescope (JWST).

The brand new research continues Professor Kobayashi’s ongoing analysis into the origin of components within the universe. As she explains, “Oxygen is likely one of the so-called alpha-elements produced by huge stars. The others are neon, magnesium, silicon, sulfur, argon, and calcium.

“Oxygen and argon have been measured with planetary nebulae, however Andromeda is so distant that JWST is required to measure different components, together with iron. In coming years, JWST and ground-based massive telescopes will preserve taking a look at Andromeda—giving additional weight to the brand new findings.”