In the study, published today in the journal Nature Astronomy, the team found that about 80% of the stars in the central region of the Milky Way formed in the early years of our galaxy, between 8 and 13.5 billion years ago. This initial period of star formation was followed by about six billion years during which very few stars were born. This came to an end with the appearance of an intense burst of star formation about one billion years ago in which, during a period of less than one hundred million years, stars with a combined mass possibly as high as a few tens of millions of suns formed in this central region.
"Conditions in the region studied during this burst of activity must have been similar to those in 'starburst' galaxies, which form stars at rates of more than 100 solar masses per year, says Nogueras-Lara, who is now based at the Max Planck Institute for Astronomy in Heidelberg, Germany. Currently, the entire Milky Way is forming stars at a rate of about one to two solar masses per year.
"This burst of activity, which must have resulted in the explosion of more than a hundred thousand supernovae, was probably one of the most energetic events in the entire history of the Milky Way," he adds. During a burst of star formation, many massive stars are created; since they have a shorter lifetime than lower-mass stars, they reach the end of their lives much faster, dying in violent supernova explosions.
This research was made possible by observations of the galactic central region made with ESO's HAWK-I instrument on the VLT in Chile's Atacama Desert. This infrared-sensitive camera cut through the dust to give us a deeply detailed image of the central region of the Milky Way, published in October in the journal Astronomy & Astrophysics by Nogueras-Lara and a team of astronomers from Spain, the United States, Japan and Germany. The impressive image shows the densest region of stars, gas and dust in the galaxy, which also hosts a supermassive black hole, with an angular resolution of 0.2 arcseconds. This means that the level of detail achieved by HAWK-I is roughly equivalent to seeing a soccer ball in Zurich from Munich, where ESO's headquarters are located.
This image is the first version of the GALACTICNUCLEUS survey. This program relied on the large field of view and high angular resolution of HAWK-I, installed on ESO's VLT, to produce a sharp and beautiful image of the central region of our galaxy. The survey studied more than three million stars, covering an area corresponding to more than 60,000 square light-years of distance from the galactic center (one light-year is about 9.5 trillion kilometers).
Additional information
This research work has been presented in the scientific papers "GALACTICNUCLEUS: A high angular resolution JHKs imaging survey of the Galactic Centre: II. First data release of the catalogue and the most detailed CMDs of the GC", published in the journal Astronomy & Astrophysics, and "Early formation and recent starburst activity in the nuclear disc of the Milky Way", which appears in the journal Nature Astronomy (doi: 10.1038/s41550-019-0967-9).
The scientific paper team published in the journal Astronomy & Astrophysics consists of F. Nogueras-Lara (Instituto de Astrofísica de Andalucía, Granada, Spain [IAA-CSIC]); R. Schödel (IAA-CSIC); A. T. Gallego-Calvente (IAA-CSIC); H. Dong (IAA-CSIC); E. Gallego-Cano (IAA-CSIC and Centro Astronómico Hispano-Alemán, Almería, Spain); B. Shahzamanian (IAA-CSIC); J. H. V. Girard (Space Telescope Science Institute, Baltimore, USA); S. Nishiyama (Miyagi University of Education, Sendai, Japan); F. Najarro (Department of Astrophysics, Centro de Astrobiología CAB (CSIC-INTA), Torrejón de Ardoz, Spain); N. Neumayer (Max Planck Institute for Astronomy, Heidelberg, Germany).
The team of the scientific article published in the journal Nature Astronomy is composed of F. Nogueras-Lara (Instituto de Astrofísica de Andalucía, Granada, Spain [IAA-CSIC]); R. Schödel (IAA-CSIC); A. T. Gallego-Calvente (IAA-CSIC); E. Gallego-Cano (IAA-CSIC); B. Shahzamanian (IAA-CSIC); H. Dong (IAA-CSIC); N. Neumayer (Max Planck Institute for Astronomy, Heidelberg, Germany); M. Hilker (European Southern Observatory, Garching, Munich area, Germany); F. Najarro (Department of Astrophysics, Centro de Astrobiología, Torrejón de Ardoz, Spain); S. Nishiyama (Miyagi University of Education, Sendai, Japan); A. Feldmeier-Krause (Department of Astronomy and Astrophysics, University of Chicago, Chicago, USA); J. H. V. Girard (Space Telescope Science Institute, Baltimore, USA) and S. Cassisi (INAF-Observatorio Astronomico d'Abruzzo, Teramo, Italy).
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