A Starburst in the Early Milky Way: A New Look at Our Galaxy’s Beginnings

The Milky Way has a long and complex history, shaped by events that happened billions of years ago. A new study led by Boquan Chen investigates an ancient period of intense star formation—what astronomers call a starburst—that took place in the early history of our galaxy. By analyzing metal-poor stars, the researchers provide new insights into how the Milky Way formed and evolved.

Clues from Metal-Poor Stars

Stars are like cosmic time capsules, preserving the chemical makeup of the galaxy when they were born. Scientists often study metal-poor stars—those with very little iron ([Fe/H] < -1.5)—because they formed when the universe was still young, before many heavier elements existed. Using data from the European Space Agency’s Gaia mission, the team examined the distribution of these stars across the Milky Way, focusing on their metallicity (iron content) and movement. They found something surprising: two different populations of metal-poor stars, one near the disk of the Milky Way and another farther above it.

A Starburst Event 13 Billion Years Ago

By analyzing how these stars move, the researchers discovered a sharp transition in their rotation speed around a metallicity of [Fe/H] = -2.0. This suggested that a major event—likely a sudden burst of star formation—had taken place. The study proposes that during the first billion years of the Milky Way’s history, a large amount of gas flowed into the galaxy’s center. This rapid gas inflow triggered a massive starburst, forming many new stars in a short period. Afterward, star formation slowed down, leading to the two distinct groups of stars seen today.

Simulating the Early Milky Way

To test their idea, the researchers used a galactic chemical evolution (GCE) model, which simulates how elements spread and evolve in a galaxy over time. Their model showed that the observed patterns in the metal-poor stars could be explained by an early starburst followed by a more gradual period of star formation. They also compared their findings with computer simulations of Milky Way-like galaxies from the Auriga project. These simulations supported the idea that early galaxies often experienced starbursts triggered by large amounts of gas flowing in from their surroundings.

Why This Matters

Understanding the Milky Way’s early history helps scientists piece together how galaxies form and evolve. This discovery provides strong evidence that the Milky Way didn’t grow at a steady pace but instead experienced bursts of rapid star formation. The study also shows how powerful modern astronomical surveys, like Gaia, are in uncovering the secrets of our galaxy’s past.

Looking Ahead

The research opens the door for future studies to investigate how this starburst influenced the later structure of the Milky Way, including its disk and halo. By studying more metal-poor stars and improving galaxy simulations, astronomers can refine their models and get an even clearer picture of our galaxy’s first billion years.

Source: Chen