Discover one of the most violent events that happened in the Milky Way
A group of astronomers, including scientists from the Instituto de Astrofísica de Andalucía in Granada, have just discovered new details about the history of the birth of the stars that form part of the Milky Way. The images of the central part of the Milky Way obtained from ESO's VLT (Very Large Telescope) telescope show that there was an intense stellar explosion that caused some 100,000 supernova explosions.
Researchers have discovered that nearly 80% of the stars in the central Milky Way were formed in the early years of the galaxy, between eight and 13.5 billion years ago. This period was followed by some 6 billion years in which very few stars were born and which were interrupted by an intense stellar burst that occurred about 1 billion years ago during a time span of less than 100 million years. The stars that formed in this central region had a combined mass possibly as high as a few tens of millions of suns. This discovery overturns what had been accepted until now, which defended that the formation of stars had been continuous.
"This explosion of activity, which must have given rise to the explosion of more than one hundred thousand supernovae, was probably one of the most energetic events in the entire history of the Milky Way," said astrophysicist Francisco Nogueras-Lara, first author of the study and attached to the Max Planck Institute for Astronomy in Heidelberg (Germany). When an explosion occurs, many massive stars form. These stars have a shorter life span than lower-mass stars, reach the end of their lives much faster, and die giving rise to violent supernova explosions.
"The conditions in the region studied during this burst of activity must have resembled those of the 'starburst' galaxies, which form stars at rates of more than 100 solar masses per year," adds Nogueras-Lara. Today in the Milky Way stars are formed at a rate of one or two solar masses per year.
The research, published in Nature Astronomy, is funded by the European Research Council and has been made possible by the HAWK-I instrument of ESO's VLT telescope in the Atacama Desert (Chile). This camera is sensitive to infrared and can see through dust clouds. With it, a very detailed image of the central part of the Milky Way has been obtained that has allowed the discovery. The image shows the densest region of stars, gas and dust in the galaxy, plus a super-massive black hole, with an angular resolution of 0.2 arc seconds. This would be comparable to watching a soccer ball in Zurich from Munich.
More than three million stars have been analysed in the study, covering an area corresponding to more than 60,000 square-light-years at a distance from the galactic centre (a light-year is approximately 9.5 billion kilometres).
