Galaxies Collide! Burst of Star Formation in Milky Way Likely Came from Cosmic Crash

The Gaia satellite observed this portion of the Milky Way, called Rho Ophiuchi. The spacecraft measured the region continuously for 22 months to pinpoint the stars' locations and velocities.
The Gaia satellite observed this portion of the Milky Way, called Rho Ophiuchi. The spacecraft measured the region continuously for 22 months to pinpoint the stars' locations and velocities. (Image credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO)

A galactic merger in our Milky Way galaxy likely produced a star "baby boom" billions of years ago, according to new research. 

Knowledge about this burst of star formation comes courtesy of the European Space Agency's Gaia satellite, which monitors the positions and velocities of stars throughout our galaxy.

The young Milky Way would have had a lot of gas available to it, but the supply diminished over time as stars formed and used up the available material. What the new research shows, however, is that the Milky Way had a steady decline in star formation during its first 4 billion years, before a burst in star formation took place.

This means that a new supply of gas must have come in, and the study's researchers suggested that supply came from the Milky Way's merger with a satellite galaxy. A merger would also explain some of the variation in star ages, masses and distances that Gaia observed, the researchers said in a statement released May 8. Additionally, it's well-known that the Milky Way is a product of past galactic mergers, and that it's on its way to colliding with the Andromeda galaxy in a few billion years, so the results match up with other scientific work on our home galaxy.

The distribution of the 3 million stars Gaia measured to detect a burst of star formation 2-3 billion years ago. (Image credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO)

The length of the star formation observed, along with the vast amounts of mass involved in the process, therefore shows the Milky Way "may have suffered an external perturbation that began about five billion years ago," lead author Roger Mor, a doctoral student in astronomy at the University of Barcelona, said in the statement. (The external perturbation was most likely the galactic merger.)

The researchers discovered this information by using Gaia to look at star distances, which allowed the researchers to pinpoint the stars' positions for the first time.

Santi Roca-Fàbrega, a cosmologist at the Complutense University of Madrid and co-author of the article, added in the statement that the observations do match up with current cosmological models. "Our galaxy seen from Gaia's eyes is an excellent cosmological laboratory where we can test and confront models at a bigger scale in the universe," he said.

The new work was detailed in April in the journal Astronomy & Astrophysics.

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: