astronomy
New type of star: Old smokers in the heart of the Milky Way
Infrared images of a red giant star about 30,000 light-years away near the center of our Milky Way Galaxy that faded and reappeared over the course of several years. photo
© Philip Lucas/University of Hertfordshire/dpa
The researchers were actually looking for stars that were still forming. But they found something completely different – a previously unknown type of star.
An international research team is searching for very young stars in the central region Milky Way unexpectedly encountered a new type of very old star. They emit dense clouds of dust and were therefore named Old Smokers by astronomers.
The emitted dust could play an important role in the formation of new stars and planets in some regions of the galaxy, the scientists report in the journal “Monthly Notices of the Royal Astronomical Society”.
What we were looking for was something completely different
“Our actual goal was to discover so-called protostars, which show enormous bursts of brightness that last for months or even many years,” explains Zhen Guo from the University of Valparaiso in Chile.
“These eruptions occur in the rotating disk of gas and dust around the newly born stars – and could complicate the formation of planets.” So far, astronomers do not know what the cause of the eruptions is. That’s why Guo and his colleagues wanted to record as many such outbreaks as possible and track them as they progressed.
In their search, the researchers used data from an observation project that has been running since 2010 at the European Southern Observatory’s Vista telescope in Chile, which measures the brightness of around a billion stars in the central thickening of the Milky Way. Vista observes infrared radiation and is therefore particularly suitable for detecting newly born stars. These are often hidden behind clouds of dust and therefore invisible to optical telescopes – but infrared radiation can penetrate the dust.
The team was successful: Guo and his colleagues identified 32 protostars with flares that increased their brightness by up to three hundred times. Many of these eruptions are still ongoing, giving researchers the first opportunity to follow the mysterious phenomena throughout their course.
Old smokers emit dust
But in addition to what they were actually looking for, the team also discovered something completely unexpected in the Vista data: ancient red stars in the heart of the Milky Way that changed their brightness in mysterious ways over the years. The researchers identified a total of 21 of these celestial objects.
They initially had no explanation for the fact that these stars were barely visible at first, but then became increasingly brighter. Further observations of seven of these objects finally provided an explanation: apparently the stars had ejected huge clouds of dense dust that dimmed their brightness.
These Old Smokers, as astronomers have dubbed the new type of star, are all located in a disk-shaped structure at the center of the Milky Way. The astronomers write that stars in this disk have a higher proportion of heavy elements than further out in the Milky Way. And that, according to Guo and his colleagues, could also be an explanation for the phenomenon. Because if there are more heavy elements present, more dust can form in the cool outer layers of the stars.
However, why the Old Smokers glow quietly for long periods of time and then suddenly emit their dust in large eruptions remains a mystery. With the help of further observations of the new stars, the researchers want to find out the cause of the dust eruptions.
The dust emitted by the old stars in the central region of the Milky Way and other galaxies could play an important role in the redistribution of heavy elements in space. These heavy elements in turn influence the formation of new stars and planets – especially rocky planets like our Earth.