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A decade-long survey of the night sky has revealed a mysterious new species that astronomers are referring to as an “old smoker”.
These previously hidden stellar objects are aging, massive stars located near the heart of the Milky Way galaxy. The stars are inactive for years and fade until they are almost invisible before belching out clouds of smoke and dust, and astronomers think that they could be involved in the distribution of elements throughout the universe.
Four studies detailing the observations were published January 25 in the Monthly Notices of the Royal Astronomical Society.
Astronomers spotted the old smoking stars for the first time during the survey which monitored nearly a billion stars in infrared light, which is invisible to the human eye.
The observations were made with the Visible and Infrared Survey Telescope, located at a vantage point high in the Chilean Andes at the Cerro Paranal Observatory.
The search for newborn stars
The team’s initial goal was to search for newborn stars, which are difficult to detect in visible light because they are obscured by dust and gas in the Milky Way. But infrared light can pass through the galaxy’s high concentration of dust to pick out hidden or faint objects.
While two-thirds of the stars were easy to classify, the rest were more difficult, so the team used the European Southern Observatory’s Very Large Telescope to study individual stars, said Philip Lucas, professor in astrophysics at the University of Hertfordshire. Lucas was lead author on one study and co-author on the other three.
As astronomers monitored hundreds of millions of stars, they tracked down 222 that had significant changes in brightness. The team determined that 32 of them were newborn stars that increase in brightness by at least 40 times, and some as much as 300 times. A large percentage of the eruptions are ongoing, so astronomers can continue to monitor how the stars change over time.
“Our main aim was to find rarely seen newborn stars, also known as protostars, undergoing massive outbursts that last for months, years, or even decades,” said the Dr Zhen Guo, Fondecyt Postdoc Fellow at the National University of Ireland, Galway. Valparaiso in Chile, in a statement. Guo was lead author on two studies, and co-author on the other two studies.
“These outbursts occur in the slowly spinning disc of material that is forming a new solar system. They help the newborn star in the center to grow, but make it more difficult for planets to form. We still don’t understand why the discs become unstable like this,” Guo said.
An unexpected stellar discovery
While observing the stars near the Galactic center, the team identified 21 red stars that experienced unusual changes in luminosity, which puzzled astronomers.
“We weren’t sure if these stars were protons starting to erupt, or recovering from a dip in brightness caused by a disk or dust shell in front of the star — or if they were older massive stars throwing off material in the phases late. of her life,” said Lucas.
The team focused on seven of the stars and compared the new data they collected with data from previous surveys to determine that the stellar objects are a new type of red giant star.
Red giants form when stars have exhausted their supply of hydrogen for nuclear fusion and begin to die. In about 5 or 6 billion years, our sun will become a red giant, puffing up and expanding as it releases layers of material and probably evaporates the planets of the solar system, although the fate of the Earth is unclear, according to NASA .
But the stars seen during the survey are different.
“These old stars sit quietly for years or decades and then they release clouds of smoke in a completely unexpected way,” said Dante Minniti, a professor in the Department of Physics at Andrés Bello University in Chile and co-author of three of the studies, i. statement. “They look very thin and red for several years, to the point sometimes we can’t see them at all.”
The stars were mostly found in the innermost nuclear disk of the Milky Way, where the stars are more concentrated in heavy elements. Understanding how smokers release elements into space could change the way astronomers think about how such elements are distributed throughout the universe.
Astronomers are still trying to understand the process behind the stars’ release of dense smoke, and what happens next.
“Material ejected from old stars plays a key role in the life cycle of the elements, helping to form the next generation of stars and planets,” Lucas said. “This was thought to happen mainly in a well-studied type of star known as a Mira variable. However, the discovery of a new material-consuming star may have wider implications for the distribution of heavy elements in the Nuclear Disc and metal-rich regions of other galaxies.”
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