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Philip Lucas/University of Hertfordshire
An artist’s illustration shows an old smoking star or aging red giant star releasing a thick cloud of smoke and dust.
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A decade-long study of the night sky has revealed a mysterious new type of star that astronomers refer to as an “old smoker.”
These previously hidden stellar objects are aging giant stars located near the heart of the galaxy, the Milky Way. Stars are dormant for decades, fading to almost invisible before belching clouds of smoke and dust, and astronomers believe they could play a role in the distribution of elements across the universe.
Four studies detailing observations published January 25 in Monthly Notices of the Royal Astronomical Society.
Astronomers observed the old smoking stars for the first time during the study that involved monitoring nearly a billion stars in infrared light, which is invisible to the human eye.
The observations were carried out with the Visible and Infrared Survey Telescope, located at a viewing point high in the Chilean Andes at the Cerro Paranal Observatory.
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 penetrate the galaxy’s high concentrations of dust to detect objects that would otherwise be obscured or faint.
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 of astrophysics at the University of Hertfordshire. Lucas was the main author of A study and co-author of the other three.
Philip Lucas/University of Hertfordshire
This illustration shows an eruption occurring in the rotating disk of matter around a newborn star.
As astronomers monitored hundreds of millions of stars, they tracked 222 that experienced notable changes in their brightness. The team determined that 32 of them were newborn stars whose brightness increases at least 40 times, and some up to 300 times. A large percentage of the eruptions are ongoing, so astronomers can continue to monitor how stars evolve over time.
“Our main goal was to find rarely seen newborn stars, also called protostars, while they are undergoing a big burst that can last for months, years or even decades,” said Dr. Zhen Guo, a Fondecyt postdoctoral fellow at Valparaíso University in Chile, in a statement. Guo was the primary author fingers studiesand co-author of the other two.
Philip Lucas/University of Hertfordshire
Astronomers used an infrared telescope to observe a star that gradually grew 40-fold over two years and has remained bright since 2015.
“These bursts occur in the slowly rotating disk of matter that is forming a new solar system. They help the newborn star in the middle grow, but hinder the formation of planets. We still don’t understand why disks become so unstable,” Guo said.
During their observations of stars near the galactic center, the team identified 21 red stars that experienced unusual changes in their luminosity that baffled astronomers.
“We were not sure if these stars were protostars initiating an eruption or recovering from a drop in brightness caused by a disk or dust layer in front of the star, or if they were older giant stars that were shedding matter in the later stages . of his life,” Lucas said.
The team focused on seven of the stars and compared the new data they collected with data from previous studies to determine that the stellar objects were a new type of red giant stars.
Philip Lucas/University of Hertfordshire
The infrared images show a red giant star, located 30,000 light years away, near the center of the Milky Way. The star faded and then reappeared over several years.
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, swelling and expanding as it sheds layers of material and likely evaporating the solar system’s inner planets, although Earth’s fate remains unclear. of course, according to POT.
But the stars detected during the study are different.
“These elderly stars remain silent for years or decades and then expel clouds of smoke in a totally unexpected way,” said Dante Minniti, a professor in the physics department at Universidad Andrés Bello in Chile and co-author of three of the studies, in a statement. “For several years they look very dull and red, to the point that sometimes we can’t see them at all.”
The stars were largely found in the innermost nuclear disk of the Milky Way, where the stars are more concentrated in heavy elements. Understanding how old smokers release elements into space could change the way astronomers think about the way such elements are distributed in the universe.
Astronomers are still trying to understand the process behind the release of dense smoke from stars and what happens next.
“Matter ejected from old stars plays a key role in the life cycle of elements, helping to form the next generation of stars and planets,” Lucas said. “This was thought to occur primarily in a well-studied type of star called the Mira variable. However, the discovery of a new type of star that sheds matter could have broader importance for the spread of heavy elements in the Nuclear Disk and in metal-rich regions of other galaxies.