In the heart of the Milky Way, a recent astronomical discovery has puzzled scientists: stars nicknamed "old smokers" for their enigmatic behavior. While their very existence was unexpected, these stars offer a cosmic spectacle never before seen in red giants.
The "old smokers" are distinguished by their ability to remain almost invisible, before suddenly releasing a "cloud of smoke". This phenomenon, observed by an international team of astronomers, was not initially aimed at finding such stars. Indeed, during a ten-year study covering hundreds of millions of stars across the sky with the VISTA telescope in the Andes of Chile, researchers aimed to identify nascent stars, or proto-stars, known for their frequent and exuberant eruptions.
Among their discoveries, which included 32 proto-stars, a major surprise awaited the astronomers: the presence, in the center of the Milky Way, of these "old smokers". Located in the Nuclear Stellar Disk, a dense, metal-rich region of our galaxy, these stars exhibit strange behavior: after a long period of inactivity, they suddenly darken, becoming so faint at times that even the telescope's infrared vision struggles to detect them. Then, without warning, they regain their original brightness.
The explanation behind these "puffs" of smoke that temporarily mask the stars from our view remains a mystery. Scientists speculate that the richness in heavy elements of this region might promote the formation of dust around the stars, dust that would then be ejected for still unknown reasons. If this theory is proved, the process could have significant importance in the dispersion of heavy elements throughout the galaxy, and beyond.
Although researchers have identified at least 21 of these "old smokers", they suspect there are many more hidden in the depths of space. This phenomenon, still under study, promises to reveal new secrets about the life's end of stars and the chemical composition of our galaxy. The results of this research were published in the
Monthly Notices of the Royal Astronomical Society.