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A decade-long search of the night sky has revealed a mysterious new type of star that astronomers have dubbed an “old smoker.”
These previously hidden stellar objects are aging giant stars located near the heart of the Milky Way galaxy. The stars have been dormant for decades, fading until they are almost invisible before erupting into clouds of smoke and dust. Astronomers think they may play a role in distributing elements throughout the universe.
Four studies detailing the observations were published January 25 in the Monthly Notices of the Royal Astronomical Society.
Astronomers observed former smoking stars for the first time during the research, which involved monitoring nearly a billion stars in infrared light invisible to the human eye.
The observations were made with the Visible and Infrared Survey Telescope at Cerro Paranal Observatory, located high in the Chilean Andes.
The search for newborn stars
The team’s initial goal was to look 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 penetrate the galaxy’s highly concentrated dust and detect hidden or faint objects.
Philip Lucas, professor of astrophysics at the University of Hertfordshire, said that although 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 examine individual stars. Lucas was the lead author of one study and co-author of three others.
While astronomers monitored hundreds of millions of stars, they also tracked 222 stars that experienced noticeable changes in brightness. The team determined that 32 of these were newborn stars whose brightness increased by at least 40 times, and some by up to 300 times. A large percentage of the explosions are ongoing, so astronomers can continue to watch how stars evolve over time.
Fondecyt Postdoctoral Researcher Dr. “Our main goal was to find newborn stars, also called protostars, which are rarely seen when experiencing a massive explosion that could last months, years, or even decades,” said Zhen Guo. He said in Valparaiso, Chile. Guo was the lead author of two studies and co-author of two others.
“These explosions occur in a slowly rotating disk of material that forms a new solar system. They help the newborn star in the middle grow, but make it difficult for planets to form. We don’t yet understand why the disks become unstable in this way,” Guo said.
An unexpected star discovery
During their observations of stars near the galactic center, the team detected 21 red stars experiencing unusual changes in brightness that surprised astronomers.
“We weren’t sure whether these stars were the first stars to begin exploding, protostars recovering from a dip in brightness caused by a disk or dust shell in front of the star, or whether they were older giant stars shedding material in late stages. of their lives,” Lucas said.
The team focused on seven of the stars and, by comparing the new data they collected with data from previous studies, determined that the stellar objects were a new type of red giant star.
Red giants form when stars run out of hydrogen supplies needed for nuclear fusion and begin to die. According to NASA, although Earth’s fate remains uncertain, in about 5 or 6 billion years, our sun will become a red giant that swells and expands as it sheds layers of material, possibly vaporizing the solar system’s inner planets.
However, the stars detected during the research are different.
“These old stars sit quietly for years and then, completely unexpectedly, they expel clouds of smoke,” said Dante Minniti, a professor in the department of physics at Andrés Bello University in Chile and a co-author of three studies. An idiom. “For a few years they look very pale and red, so much so that sometimes we can’t see them at all.”
The stars are largely found in the innermost nuclear disk of the Milky Way, where heavy elements are more concentrated. Understanding how former smokers released elements into space could change how astronomers think about the way such elements are distributed in the universe.
Astronomers are still trying to understand the process behind stars emitting dense smoke and what happens next.
“Matter ejected from old stars plays an important role in the life cycle of elements and helps form new generations of stars and planets,” Lucas said. “This was thought to occur primarily in a well-studied type of star called the Mira variable. But the discovery of a new type of star that ejects matter may be of greater significance for the diffusion of heavy elements in the Nuclear Disc and metal-rich regions of other galaxies.”
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