Analysis of Gaia Satellite Data Reveals Severe Star Formation Burst in Milky Way in the Past

A group headed by scientists from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB, UB-IEEC) and the Besançon Astronomical Observatory analyzed data from the Gaia satellite and has discovered that an intense star formation burst took place in the Milky Way nearly two and three thousand million years ago.

During the study, over 50% of the stars that formed the galactic disk may have been originated. The study outcomes have been realized from the combination of the colors, distances, and magnitude of the stars measured by Gaia using models that predict their distribution in the Milky Way Galaxy. The research has been reported in the Astronomy & Astrophysics journal.

Quite similar to the way a flame fades when the gas in the cylinder is emptied, the stellar formation rhythm in the Milky Way, fueled by the deposited gas, should decrease gradually and in a continuous manner until all the existing gas is used up. The outcomes of the study demonstrate that even though this was the process that occurred in the first 4000 million years of the formation of the disk, an intense star formation burst, or “stellar baby boom”—as mentioned in the article published in the Nature Research Highlights—reversed this tendency.

The merger with a gas-rich satellite galaxy of the Milky Way could have delivered new fuel and restarted the stellar formation process, in a fashion similar to changing a gas cylinder. This mechanism would elucidate the distribution of ages, distances, and masses that are calculated from the data collected from the European Space Agency Gaia satellite.

The time scale of this star formation burst together with the great amount of stellar mass involved in the process, thousands of millions of solar mass, suggests the disc of our Galaxy did not have a steady and paused evolution, it may have suffered an external perturbation that began about five billion years ago.

Roger Mor, Researcher, ICCUB

Mor is also the first signer of the article.

“We have been able to find this out due having—for the first time—precise distances for more than three million stars in the solar environment,” stated Roger Mor. “Thanks to these data—he continues—we could discover the mechanisms that controlled the evolution more than 8-10 billion years ago in the disc of our Galaxy, which is not more than the bright band we see in the sky on a dark night and with no light pollution.” Similar to what happens in various research fields nowadays, these outcomes have been made possible by the availability of the combination of a great deal of data with unmatched precision, as well as the availability of a great deal of hours in computing in the computer facilities funded by the FP7 GENIUS European project (Gaia European Project for Improved data User Services)—in the Center for Scientific and Academic Services of Catalonia (CSUC).

As predicted by cosmologic models, the Milky Way galaxy would have been enlarging due to the merger with other galaxies, a fact that has been put forward by other studies with the help of the Gaia data. One of these merges could be due to the intense star formation burst that was observed as part of this study.

Actually, the peak of star formation is so clear, unlike what we predicted before having data from Gaia, that we thought necessary to treat its interpretation together with experts on cosmological evolution of external galaxies.

Francesca Figuerars, Lecturer, Department of Quantum Physics and Astrophysics, University of Barcelona

Figuerars is also an ICCUB member and a signer of the article.

Santi Roca-Fàbrega, an expert on simulations of galaxies similar to the Milky Way from the Complutense University of Mardid and also signer of the article, stated that “the obtained results match with what the current cosmological models predict, and what is more—he continues—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.”

Gaia Mission Until 2020

This research has been performed with the second release of the Gaia mission, published a year ago, on April 25^th, 2018. According to Xavier Luri, director of ICCUB and also signer of the article, “The role of scientists and engineers of the UB has been essential so that the scientific community enjoys the excellent quality of data from the Gaia release.”

Over 400 researchers and engineers from across Europe are part of the consortium in charge of preparing and validating these data. “Their collective work brought the international scientific community a release that is making us rethink many of the existent scenarios on the origins and evolution of our galaxy,” noted Luri.

Within a year, over 1200 peer-review articles published in journals reveal the before and after Gaia in nearly all fields of astrophysics, from the latest detection of new asteroids, new stellar clusters, to the confirmation of the star extragalactic origin in our Galaxy, going about the calculus of the mass of the Milky Way galaxy and the discoveries that demonstrate that compact stars get solidified gradually.

“The satellite continues to operate optimally and this July the five nominal years of scientific operation will be completed,” stated Carme Jordi, UB researcher and member of the Gaia Science Team, the scientific advisor body of the European Space Agency (ESA) for this mission. The extension of the mission until late 2020—one more year than anticipated before—has been approved by the ESA, and engineering teams predict that there is sufficient fuel to continue working until 2024. “There is no doubt this mission has passed a technological unprecedented challenge in space missions of all time,” concluded Carme Jordi.